Benjamin Krupp

"Blah, blah, blah, blah, blah!"

- Mr. Krupp

Benjamin "Benny" Krupp is the principal of Jerome Horwitz Elementary School. He is one of the two secondary antagonists (alongside Melvin Sneedly) of the Captain Underpants franchise. He has a long history with two fourth grade students named George and Harold due to their constant pranks, wisecracks, and comic books. Benjamin's alter ego is Captain Underpants, which he is totally unaware of.

He and his alter ego are voiced by Ed Helms in Captain Underpants: The First Epic Movie, Nat Faxon in The Epic Tales of Captain Underpants, and Len Forgione in the Sound-O-Rama Audiobooks.

Characterization
Benjamin is an unbelievably hot-tempered and nasty principal. He distributes detention slips to any student for even a minor infraction, just so long as they are unfortunate enough to cross his path. In one case, he punished George and Harold by not allowing them to have cafeteria food and makes them bring their own lunches in his office to keep an eye on them, even though he had no actual proof (however, given that the two were responsible it was justified). He once blackmailed George and Harold into doing all his daywork and even giving them extra homework in exchange for not getting "killed every day for the rest of their lives". He even tore out the last seven pages of the book, "How The Grinch Stole Christmas", and make the plot sound more realistic, assumingly cutting the book off right before the Grinch's heart grows.

His hatred towards George and Harold reaches the point where he tries to find a way to get rid of them (even if it meant that they would be killed) or (to a lesser extent) separate them somehow. In the ninth book, he was greatly happy that Tippy Tinkletrousers was going to destroy the duo and willingly told the Turbo Toilet 2000 where George and Harold hang out in the eleventh book, so they would be gone. Also when George and Harold flunked their "Super Secret" tests, Benjamin and the faculty were greatly overjoyed that Harold flunked the fourth grade because he and George would no longer be in the same grade and thus have completely different paths.

Despite being really nasty, Benjamin does show forms of kindness. He will readily punish anyone who is bullying his nephew Kipper Krupp. Kipper just needs to yell out for his uncle and explain to him what happened, though Kipper usually makes it look like he was bullied in front of his uncle (For example: after Kipper punched a little girl in the stomach, Kipper told his uncle that the girl's stomach hit his first). Benjamin always believes his nephew's claims no matter how illogical they seem.

Benjamin also cares about his job, as he feared he would lose his job in the second book after seeing the school destroyed by the Talking Toilets until George and Harold managed to fix the school. Additionally, when Tippy Tinkletrousers unintentionally changed the past, he unintentionally caused Benjamin to be fired from his post as principal. Mr. Krupp was shown shedding a tear as he was walking away with his "Krupp Stuff." With that happening also meant that in a few more years, he himself would never get hypnotized by George and Harold and become Captain Underpants, and the villains from the first three books would take over the world, end up in a rough battle which eventually resulted in the world’s destruction.

Pre-Captain Underpants
Years before he became Captain Underpants, he would readily punish anyone who was "bullying" his nephew: Kipper Krupp. Kipper just needed to yell out for his uncle and explain to him what happened, though he usually made it look like he was bullied in front of his uncle. For example, when Kipper punched a little girl in the stomach, Kipper told his uncle that the girl's stomach somehow hit his fist first. Benjamin always believed his nephew's claims no matter how illogical they seemed.

When George saved Harold from Kipper and his cronies, the two became best friends. Unfortunately, they weren't aware that Kipper was Mr. Krupp's nephew, so Mr. Krupp arrived and sent the two to detention for "bullying Kipper."

11 days later, Mr. Krupp was unintentionally beaten up by his own nephew and his friends while escaping from the school due to a blackout.

The Adventures of Captain Underpants
Benjamin is an unbelievably hot-tempered and nasty principal. He distributes detention slips to any student for even a minor infraction, just so long as they are unfortunate enough to cross his path. e vows to get them one day ("one day very very soon" he claims).

The next day, George and Harold hear an announcement over the school's intercom. They are wanted in Mr. Krupp's office. Once inside, He shows the two boys that he set up video cameras all over the school, and had caught every single one of George and Harold's pranks on tape. After the tape is over, everyone is silent for a while. Then, George gets the courage to speak up and asks what Mr. Krupp is going to do with the video. Mr. Krupp thinks about it, and decides that he should show it to the school board or George and Harold's parents, but he ultimately decides to show it to the football team so they can see who ruined their big game. George and Harold beg and plead Mr. Krupp to spare them as the football team will kill them for the rest of their lives if they do find out the truth. Mr. Krupp decides not to show the video, as long as George and Harold promise to follow his conditions. Mr. Krupp takes out a stack of paper with countless chores and behavior rules for George and Harold to follow. He also mentions they MUST follow the list exactly; otherwise he will show the video to the football team. The next day, George and Harold spend their entire day doing chores for Mr. Krupp, behaving nicely, and completing stacks of extra homework.

After taking in the homework, George states he has an idea that can could get them out of this situation. George reveals that he had bought a 3-D Hypno-Ring which they could use to make Mr. Krupp hand them the video and forget that this whole mess ever happened. After 4-6 weeks of back-breaking labor, George and Harold finally get the ring via the mail. After purposely making themselves late for chores and school, Mr. Krupp gets them into his office and demands where were they this morning. George and Harold state they were going to show the new ring they got. George then uses the 3-D Hypno Ring to hypnotize Mr. Krupp into handing over the incriminating video. Harold replaces it with one of his little sister Heidi's Boomer the Purple Dragon sing along videos. As they look in the cabinet on what Mr. Krupp had confiscated from the boys and other people over the yrs, they discover some good stuff including the Captain Underpants comics they wrote from the previous yrs. They began to reminisce the comic books by reading. Hours later, they realized it was getting close to lunch time as they were preparing to leave that noticed Mr Krupp still in a trance, so they decided to wait and play around. They then begin fooling around with the ring hypnotizing Mr Krupp thinking he is a chicken then later a monkey. And then lastly, they get an idea after looking at the comic and George hypnotizes Mr. Krupp to act as if he were the Amazing Captain Underpants. Mr Krupp began removing his toupee and clothing and takes of the curtain tying it to his neck and he is seen dressed like Captain Underpants yelling the battle cry "Tra La Laaa!". George and Harold look at him and began laughing hard to their distress. As they stopped laughing to take one more look at him, they saw he was gone. They then heard him outside doing the battle cry again and as they look out the window they saw Mr Krupp dressed as Captain Underpants running outside into the city of Piqua

Atfer George, Harold, and Captain Underpants return to Mr. Krupp's office. They give Captain Underpants Mr. Krupp's clothes along with an extra pair of underpants to dress up like Mr. Krupp, so that nobody in the school would recognize him. Captain Underpants them gives them the meanest look to them like the boys asked him to do to look like Mr. Krupp. The boys try to figure out how to return Mr. Krupp to his normal self, but they've lost the instruction manual for the 3-D Hypno-Ring. They try several times to hypnotize Captain Underpants back into Mr. Krupp, but the methods do not work. As a last resort, George tries dumping water on Mr. Krupp's head. It works, and Mr. Krupp returns to his angry self, resolving to give the video to the football team after all though George and Harold are surprisingly very happy to see Mr. Krupp again. George finds the instruction manual to the 3-D Hypno-Ring in his shirt pocket, but he and Harold throw it away as they believe they do not need it anymore. As it turns out, the team enjoyed the Sing-A-Long video so much that they change their name from the Knuckleheads to the Purple Dragon Sing-A-Long Friends.

George and Harold go back to their goofy ways with nothing that is threatening to their lives. Unfortunately from this point on, whenever anyone snaps their fingers, Mr. Krupp transforms into Captain Underpants. Ms. Ribble is then shown snapping her fingers after George and Harold disrupt the class with their jokes, Mr. Krupp who was passing by with a cup of coffee unfortunately hears the sound of fingers snapping and drops his cup of coffee being in a trance, becomes Captain Underpants again and runs out of the school to fight crime. Harold and George hear his battle cry and both look outside to see that Captain Underpants has return once again. Much to their surprise, both respond to this with "Oh No!" and "Here we go again!" respectively as they thought it was over with Captain Underpants, it wasn't. The adventure was only just beginning.

Captain Underpants and the Attack of the Talking Toilets
Jerome Horwitz Elementary School is going to hold its second annual Invention Convention. Students George and Harold remember how at the last Invention Convention, they pulled a prank on the school that caused everyone to be super-glued to their seats. This year, however, because the winners of the Invention Convention get to be principal for a day, they decide to take it seriously.

Unfortunately, their Principal, Mr. Krupp wants to avoid a fiasco like last year's and bans George and Harold from the Invention Convention, forcing them to stay in the study hall all day. They decide to secretly sabotage everyone's inventions in revenge after realizing that this isn't fair. Thanks to George and Harold, the Invention Convention is a disaster and everyone in the school gets covered in slimy goo from the sabotaged inventions such as a dog washer shooting black ink at everyone instead of water at the dog, eggs shot from a shooter instead of ping-pongs and a sack of pudding from a volcano detector. The convention is called off and Mr. Krupp thought that he put George and Harold in Study Hall. However, Melvin Sneedly breaks his promise and tattles on George and Harold. As punishment, Mr. Krupp puts George and Harold in detention for the rest of the year. From now on they must write a sentence he wrote on every chalkboard in the detention room completely within 2 hours. He also threatens them if any of them leave the detention room for any reason before their 2 hours are up, he'll suspend both of them.

George and Harold quickly finish their detention work thanks to some rods that they created in George's dad's workshop. They then start to write a comic called "Captain Underpants and the Attack of the Talking Toilets" in which the Amazing Captain Underpants defeats millions of vicious talking toilets and their leader, the Turbo Toilet 2000. George suggests making copies of their new comic book for tomorrow, but Harold states they can't do that since Mr. Krupp will suspend them if he finds they had left. George states they'll just have to stay out of his sight.

George and Harold however find out there are teachers in the teachers' lounge, so that means they can't get to the copy machine. George and Harold then remember the invention Melvin made and they decide to use that to make copies of their comic book George and Harold still think that Melvin just crammed a mouse in there to fool them.

Unfortunately, the PATSY 2000 really does turn two-dimensional objects into three-dimensional objects, so the evil, vicious talking toilets come to life. George and Harold run out of the gym, but they get caught by Mr. Krupp for leaving the detention room and he declares they are suspended. They try to explain what occurred in the gym, but Mr. Krupp doesn't care or listen since they're suspended. He orders them to get out of the school for good and take their stuff with them. Before George and Harold can leave, the other teachers get the news and decide to notify their parents and throw a party in the gym for having George and Harold suspended. George tries to stop them from opening the door, but they don't listen, due to the fact that George and Harold are suspended. Once Kenny B. Meaner opens the door, one toilet gets out and swallows him. The toilets break out of the gym and attack everyone in the school. Thanks to Tara Ribble snapping her fingers at a toilet, Mr. Krupp turns into Captain Underpants

Atfer The Incredible Robo-Plunger comes to life from the machine and defeats the Turbo Toilet 2000. The duo gets their principal out of the TT 2000 and he asks what happened to the school and the teachers since everything is seemingly destroyed. Harold realizes that Captain Underpants must have gotten hit by the toilet water in the Turbo Toilet 2000 which caused him to become Mr. Krupp again. After George and Harold give his clothes and toupee back so he can dress, Mr. Krupp believes he is ruined as he will be held responsible for the mess and lose his job for that. George says they can repair the school, but they want him to cancel their detention and suspension as well as make them principals of the day. Mr. Krupp agrees to this, but only if they can do all that. After giving the Robo-Plunger the necessary commands, he repairs all the damage and takes all the evidence to Uranus with the command never to return. The teachers all believe the events regarding the attacking toilets were just a dream. In return for fixing the school, George and Harold's detention and suspension are canceled and they get to be principals for the day.

As the principals, they hold an all-day carnival for all the students and put the teachers (and Melvin Sneedly for his tattling) in detention. After telling Mr. Krupp that they sold most of the school's furniture to pay for the carnival, Krupp gets angry and they run away for their lives

Captain Underpants and the Invasion of the Incredibly Naughty Cafeteria Ladies from Outer Space (and the Subsequent Assault of the Equally Evil Lunchroom Zombie Nerds)
The lunch ladies get mad at Mr. Krupp and quit (because he can't punish George and Harold because there's no proof they did anything wrong). He said that it was not his birthday. Mr. Krupp wonders where he is going to find three new lunch ladies by tomorrow morning.

Zorx, Klax, and Jennifer, badly disguised as humans, come in and take the open lunch lady job. Mr. Krupp is happy that the problem is out of the way now. He then calls George and Harold via the intercom and tells them to come to his office. They do so and Mr. Krupp punishes the duo by forbidding them from having any cafeteria food even though he clearly knows he has no proof they were responsible for the disaster that happened the day before. He states George and Harold from now have to pack their own lunches and eat in his office so he could keep an eye on them.

The next day, George and Harold bring their lunches to Mr. Krupp's office for lunch as per what Mr. Krupp told them. After Mr. Krupp is disgusted by the food that George and Harold are eating, he leaves for some fresh air. George and Harold decide to go change the lunch menu while he is out. When they arrive at the sign, they see someone else has already altered the menu. They then see that the students and staff have been turned into Zombie Nerds. George and Harold then sneak into the kitchen and discover the cafeteria ladies are really aliens who have just fed Evil Zombie Nerd Milkshakes to the students and staff which is why almost everyone in the school has turned into a zombie nerd. George and Harold learn of the spacemen's plans to feed super evil rapid growth juice to the zombie nerds tomorrow to make them huge and evil, so that way it would be easier to conquer Earth. George and Harold steal the growth juice and try to get rid of it by pouring it out the window, but they unintentionally pour it on a dandelion.

When the boys prove to Mr. Krupp that the lunch ladies are aliens and that everyone has been turned into Zombie Nerds, however, Mr. Krupp laughs at them assuming they were lying. So he calls Edith Anthrope into his office and she comes as a Zombie Nerd and takes a huge bite of Mr. Krupp's walnut made desk. As he sees this happen he is in shock. George and Harold then take Mr. Krupp into the lunchroom but an alien disguised as a lunch lady sneaks behind and grabs Harold as he runs off accidentally pulling off the Alien's gloves. One of the aliens snaps his tentacle (a physical impossibility as noted by Harold) at them,

After the dandelion is defeated, George wonders how to get the zombie nerds back to normal. Harold suggests using the anti-evil zombie nerd juice to fix the problem. George notes that he was hoping for something more dramatic, but as they are running out of pages they should do it. Mixing anti-evil zombie nerd juice with root beer and having all the zombies drink it, they turn everyone back to normal, but not before getting the Captain to dress back up like Mr. Krupp and pouring water on his head.

Something has changed about Mr. Krupp though because he drank the super-power juice, so now whenever he becomes Captain Underpants, he can fly and use other superpowers, thus making it harder for George and Harold to keep tabs on him

Captain Underpants and the Perilous Plot of Professor Poopypants
the kids in Jerome Horwitz Elementary School are going on a field trip to the Piqua Pizza Palace. While George and Harold are waiting to get on the bus, they decide to change the school sign, until Mr. Krupp catches them "red-handed" since he has been hiding in the bushes next to the sign and thinks their sign changing is rude and offensive. As the boys' punishment, they are banned from the field trip and have to spend the whole afternoon cleaning up the teachers' lounge. The teachers laugh at them. Harold becomes saddened they won't get any fun, however George claims they can still have fun and comes up with an idea involving a ladder, a bag of powdered paste and a box of styrofoam packing pellets.

The two boys start to create a prank as payback against the teachers. First, they tape the water nozzle of the sink, to make it on when the water runs, second they fill powder of paste on the wings of the ceiling fan. Finally, they fill the fridge with millions of foam pellets.

When the students finally come back and go home, the teachers except Mr. Fyde (who is on bus duty) spend their time taunting at George and Harold, saying that they missed a good field trip. Mr. Meaner says that he was going to bring back a pizza, but, he ate it on the bus. When the teachers finish taunting the boys, they go off to the teachers' lounge. When the teachers go into the lounge to relax, they fall into George and Harold's trap. The teachers end up looking like abominable snowmen (they are covered with foam pellets that are stuck to their bodies due to them being wet and covered in powdered paste) and they run, scream, and chase George and Harold down the hall with Mr. Fyde looking at the window.

The next day, their old science teacher, Morty Fyde quits because he thought he had cracked up. First, he says a toilet ate him. Then he says that later he started hearing dogs and cats in his classroom, then he imagined the school got flooded with sticky green goo, and finally, he saw the other teachers chase George and Harold down the hall as "abominable snowmen". Mr. Krupp says that can all be explained as George and Harold's doing, but Mr. Fyde also insists that he saw some fat bald man in his underwear fly out a window (obviously Captain Underpants) which makes Mr. Krupp realize he has gone crazy since he has no proof that is George and Harold's doing. As Mr. Fyde dances in joy, Mr. Krupp wonders where he is going to find a new science teacher on such short notice. Later Atfer destroys the last of Professor Poopypants' credibility with the students and drives him crazy (after he found a copy of the comic in the hallway).

Using his enlarging machine, he makes the gerbil machine as large as a tall building and then gets inside. He then shrinks the school and holds them hostage. He then unveils his plan to force everyone in the world to change their names so everyone will have a silly name instead of a normal one, and anyone who refuses will be shrunk. Professor Poopypants does this first on Mr. Krupp, who becomes Lumpy Pottybiscuits. All the children find this funny, until Professor Poopypants forces them to use the chart to change their names as well. This leaves the students and staff to be quite shocked and almost horrified at their new names

Once Professor Poopypants is defeated, everyone gets their names back. The boys use the shrinking and enlarging machines to get themselves, the school and Captain Underpants back to normal size. Then Captain Underpants gets dressed back up like Mr. Krupp before being soaked with water by Harold who was playing with the hose, turning him back to his old nasty self again.

Captain Underpants and the Wrath of the Wicked Wedgie Woman
Once inside the office with all their things, Ms. Anthrope, the school secretary, tells them that Mr. Krupp is on the phone and orders them to copy the "Friday Memo" for her and makes the boys run some errands by letting them pass out "Friday Memo" (a weekly newsletter that shows the events of the upcoming week) to the entire school while she goes out to lunch. George moans and Ms. Anthrope tells them to deal with it. Before that, they made their own Friday Memo by using Ms. Anthrope's computer (since it was still on) to change a few events. They begin handing out copies of this memo when Mr. Krupp sees them, but they are able to avoid any suspicions without saying that Ms. Anthrope told them to give out the memos. Harold then tricks Mr. Krupp into signing the card claiming they are going to give it to Ms. Ribble. Mr. Krupp sees nothing wrong there and writes "Signed Mr. Krupp" on the inside of the card.

Later on, when Mr. Krupp learns about them changing letters on the sign and their comic book that they made about Ms. Ribble, he puts them in detention. They defiantly say they won't give Ms. Ribble her card. Mr. Krupp steals the card and says he'll give it to her personally. The boys secretly smile at how effective their use of reverse psychology was.

Meanwhile, Ms. Ribble's retirement party gets off to a bad start and only gets worse. She makes the whole class sing a song about her and later eat chunky tofu ice cream (by which time it has melted as she was preoccupied screaming at the boys for singing out of tune). She then receives the cards that the children made for her and several are torn to pieces (Ms. Ribble asked the students to draw a butterfly on their cards; some of the students accidentally drew polka dots on their butterflies and one boy drew a smiling sun on his card, resulting in him having to stand in the corner). Mr. Krupp gives Ms. Ribble the card, which reads "Your one hot mama! on the front and inside it reads "Will you marry me? Signed, Mr. Krupp." The other teachers assume that Ms. Ribble agrees, and on Saturday, the wedding is to be held in the school auditorium. For the 5 days before the wedding, each day ends up with something weird going on on that day (On Monday, the students do not turn up because of a "lack of interest"; on Tuesday, they turn up in their pajamas and picking their noses; on Wednesday, the students wear expired egg sandwiches on their heads and mustaches drawn on their faces in permanent marker; on Thursday, the students engage in a food fight while the football team lay waste to the teacher's lounge; on Friday, the students turn up for their class photos dressed as bees). Mr. Krupp is too shocked by the whole wedding thing to admit the truth that he doesn't want to marry her.and says “B-B-Bubba bobba hob-hobba-hobba wah- wah” George and Harold insist that the wedding should be in their math test schedule, which is on Monday.

At the wedding, while the orchestra is playing music, the rabbi of the wedding approaches the duo and states he already heard about them and warns that he doesn't want them doing any pranks at the wedding. George and Harold have made it official to him they have no tricks planned (for once). On the altar, just before they get married, Ms. Ribble breaks up with Mr. Krupp, saying that despite liking all of his cruelty she couldn't marry him because he has a funny-looking nose (the joke is that the two of them have identical noses). Mr. Krupp is angry and says he never wanted to marry her anyway; it was just a trick of George and Harold's. Due to that, Miss Ribble totally goes berserk and ruins the wedding. Ribble tries to attack the boys, but they luckily escape when the cake splats on Ms. Ribble. When Wedgie Woman kidnaps the boys and uses her super-powered intelligence to build robot copies of the two boys, Robo-George and The Harold 2000. George thinks the Extra Strength Super Power Juice must have soaked into her brain. The robots are equipped with Spray Starch to take away Captain Underpants' powers. They are then sent to Jerome Horwitz Elementary School.

The robots pose as George and Harold, except the two of them behave perfectly much to Mr. Krupp's dismay because he assumed the boys were faking good behavior as a prank on the teachers. During soccer practice, Harold 2000 kicks the ball through the page of the book and gets in trouble by Mr. Krupp but when Mr. Krupp snaps (literally) at Harold 2000, he turns himself into Captain Underpants.

Before Captain Underpants is about to send Wedgie Woman to jail, but George and Harold tell him they can handle her. They then tell him to go put some clothes on and splash water on his face and Captain Underpants complies

Captain Underpants and the Big Bad Battle of the Bionic Booger Boy - Part 1: The Night of the Nasty Nostril Nuggets
the school principal, Mr. Krupp, comes marching into the office in a particularly foul mood. He stops beside Miss Anthrope's desk, huffing and puffing, and asks for his coffee. Miss Anthrope responds "Get it yourself, tubby!" and Mr. Krupp tells her he doesn't need her lip today and demands his coffee right now. Edith instead asks for him to get her a cup, too, while he's at it. Mr. Krupp screams in frustration and grabs a newspaper, heading toward the faculty restroom. After getting pranked with a Squishy by Ms. Ribble, he storms out of the door and vows to get George and Harold, but Ms. Ribble laughs that she actually did it, and introduces the Squishy as the latest fad. Mr. Krupp, however, doesn't believe her, and searches for the two in the cafeteria. On the way he notices many other victims in the hallway that have fallen to the Squishy (mostly first, second, third, fifth, and sixth graders) complaining about ketchup stains on their lower clothing. Mr. Krupp then yells at George and Harold that he got ketchup in his underpants as well as half of the kids in the school. George and Harold protest they never did any of those pranks despite demonstrating it and some of the fourth graders support them. Unfortunately, Melvin does not agree with any of them and proudly tattles they taught the prank to the other fourth graders during demonstration speech day. Mr. Krupp then thanks him for the proof and points George and Harold to the detention room as punishment.

Atfer Melvin became The Bionic Booger Boy Mr. Krupp is put as a substitute, but is shocked to find almost everyone wearing raincoats and umbrellas. He demands an explanation for this before Melvin sneezes. Mr. Krupp returns a few moments later with fresh clothes, a raincoat and an umbrella. When Mr. Krupp tells them they are going on a field trip to Snoddy Bros. Tissue Factory, Melvin starts speaking like Frankenstein and declares out "Me no like tissues!", shocking all of the other students.

When the class visits the tissue factory, they take a tour though Melvin is the only one that is terrified. After the tour, Mr. Snoddy offers to give everyone tissue packs. Melvin refuses (he calls the tissues "bad magic"), but Mr. Snoddy assures him that everyone loves them and that these tissues can really help wiping out mucus. He then throws a couple onto Melvin, but this causes Melvin to become gigantic and evil as a natural defense against the tissues (as well as the Flexogromnic-steel in Melvin's endoskeleton). Melvin's growth and angers destroys the building and the various things surrounding the building and he kidnaps Miss Anthrope before storming out to the city..

George and Harold hid behind a window curtain at this time and later Mr. Krupp hid with them behind the curtain, As George explains that there is only one person who can save Mr. Ribble, must to Mr. Krupp's dismay as to who that person could be, George snaps Mr. Krupp into Captain Underpants to save the day.but atfer The water from the kisses unfortunately turns him back into Mr. Krupp and he gets caught by the Bionic Booger Boy when he demands an explanation from George and Harold, on why he is in his underwear. George and Harold try to get him to become Captain Underpants again through finger snapping, but due to Mr. Krupp's face still being covered by the slobbery kisses the snaps have no effect. Melvin swallows Mr. Krupp whole and then he goes for George and Harold.

after He then falls unconscious onto the ground with news people telling the story right next to his unconscious body. Melvin's parents, who are scientists, come in and pledge to try to help turn their son back to normal. By George's suggestion, they reverse the batteries in the Combine-o-Tron 2000 though it was only to prove to George that it will not work. The process somehow surprisingly works, and Melvin and Mr. Krupp are brought back, with the robotic booger globs flying off and landing on three building walls. They are unfortunately combined together for some reason, so Mr. Sneedly fires another blast and they are seemingly back to normal. But Mr. Krupp and Melvin's bodies are switched.

However, Mr. Krupp and Melvin start acting strange, with Mr. Krupp claiming credit for building the Combine-o-tron 2000, and saying, "You guys are so immature!" and Melvin giving punishments to George and Harold and claiming will punish them so badly that their kids will be born with detentions. He also says to George and Harold "In my office, PRONTO!" The robotic booger globs then come to life and then the Robo-Boogers destroy the Combine-o-Tron 2000, causing Melvin's parents to flee for their lives. The three Ridiculous Robo-Boogers then chase Melvin, Mr. Krupp, George, Harold, and Sulu

Captain Underpants and the Big, Bad Battle of the Bionic Booger Boy - Part 2: The Revenge of the Ridiculous Robo-Boogers
The three Robo-Boogers, Carl, Trixie and Frankenbooger, chase our heroes through town until they are cornered in an alley. They are about to destroy the four heroes when Sulu swallows them and then spits them into outer space. As everyone prepares to go home, it becomes obvious that there was a mistake with the Combine-o-Tron 2000, and now Melvin and Mr. Krupp have switched bodies. Several jokes are made with this outline, including "Kruppy the Kid" (Mr. Krupp in Melvin's body) roars and Ms. Anthrope to give him coffee or he would fire her. Seeing only a fourth grader, Ms. Anthrope gives him a wedgie. As for "Mr. Melvin" (Melvin in Mr. Krupp's body), he is also the basis of some abuse as he runs to hug his mother, who only sees a guy in his underwear coming to give her a hug, and promptly and ruthlessly assaults him with her purse.

After these incidents, George and Harold discover the mix up and explain it to Mr. Melvin and Kruppy the Kid. Mr. Melvin notes he could solve this problem right away if he still had his Combine-O-Tron 2000, but the Robo-Boogers smashed it in the last book. Understanding they'll need to use that invention to get everything back to normal, Kruppy the Kid orders Mr. Melvin to build a new Combine-O-Tron, but Mr Melvin says that will take six months. Kruppy yells at Mr. Melvin he has got a school to run. Mr. Melvin apologizes and says building a cellular combiner is extremely difficult. It is not easy like building something like a robot, a time machine, or a PATSY. George suggests making a time machine to get the Combine-o-Tron back. Struck with what was originally George's idea, Mr. Melvin snaps his fingers. But oddly, Kruppy the Kid becomes Captain Underpants, his alter ego and the superpowers somehow following Mr. Krupp into Melvin.

When "Kruppy the Kid" (in Melvin's body) turns into Captain Underpants, George and Harold are forced to tell the secret of Captain Underpants to "Mr. Melvin",

Atfer Melvin does get his comeuppance when the people Mr. Krupp and Captain Underpants bugged while they were in Melvin's body (Miss Anthrope, the football team, 2 old ladies, and 3 skateboarders) come back for revenge on him. They then chase him down into the sunset. As George and Harold leave back to their treehouse, they use a water fountain to splash water on Captain Underpants' face and return him to his Kruppy old self (without getting to get dressed).

Captain Underpants and the Preposterous Plight of the Purple Potty People
The book first starts off with a rant about how grown-ups (such as your parents) encourage something initially when you are very young and discourage it greatly as you grow older. Then it goes to the staff of Jerome Horwitz Elementary School who are anything but trustworthy are extremely cruel to children. However, George and Harold manage to outsmart them frequently since they aren't very bright.

Later The duo and Crackers managed to escape the evil duo that was following them, They go to Nasty Mr. Krupp's house (which Good George and Good Harold covered in toilet paper at an earlier point) and knock on his door. Right after Nasty Mr. Krupp answers, Good George and Good Harold quickly snap their fingers to turn Nasty Mr. Krupp into Captain Underpants. but when Good Harold states that nothing can go wrong, the worst thing is that something can go wrong, this causes a rainstorm to turn Nice Mr. Krupp back into Captain Blunderpants and Captain Underpants is turned back into Nasty Mr. Krupp. Good George and Good Harold try snapping their fingers, but the snaps have no effect on either Nasty Mr. Krupp or Captain Blunderpants as the rain is pouring too hard on them. Nasty Mr. Krupp can't figure out how he got outside, so he goes back to his soggy toilet paper covered home to get back to bed not contributing to the plot of what is happening around him.

Captain Underpants and the Terrifying Re-Turn of Tippy Tinkletrousers
As George and Harold are being taken away by the cops, the cops stop by Mr. Krupp's house where he is seen taking out the trash after cleaning the house from the wet soggy toilet paper. The cops rush and handcuff a confused Mr. Krupp. After their court date, George, Harold, and Mr. Krupp aka Captain Underpants were arrested and were sent to jail. George and Harold are sent to the Juvenile Hall while Mr. Krupp was sent to the Piqua State Penitentiary. The 3 were actually framed and mistaken for Evil George Beard, Evil Harold Hutchins, and Captain Blunderpants's evil antics causing chaos in the town of Piqua.

One autumn afternoon, Tippy (who is also a prisoner from the fourth book) is tasked to build a statue of Warden Gordon Bordon Shmorden who is the chief jailer of the prison, Tippy does the task but instead builds "a giant robot suit". Krupp notices Tippy and he remembers and confronts him for what happened the last time when he shrunk the school and make everyone change their names. However, Krupp does not remember that he as Captain Underpants was the one to put a stop to Tippy's reign of terror that day.

On the day of the 10th Anniversary of the Penitentiary, Tippy presents his robot suit to Gordon Shmorden, he reveals his work and climbs on to the suit and freezes everyone in his way (the same suit used at the very end of the eighth book). Tippy then grabs Mr. Krupp and forces him to spill the information of Captain Underpants and to give him the information of George and Harold whereabouts. Tippy soon finds George and Harold and puts Mr. Krupp down, wanting information of Captain Underpants. Krupp picks on them telling them they were in a lot of trouble. Seeing that they were in danger of Tippy plotting his revenge, George and Harold act fast and snap their fingers at Mr. Krupp who turns into Captain Underpants

When Tippy and his Robo-pants appear Five Years Ago. Due to Tippy's dialogue with, Kipper and his friends while it was still dark, they mistakenly thought that it's the haunted pants of Wedgie Magee and become insane. Tippy then travels four years into the future when George and Harold were about to be arrested in Book 8. Unbeknownst to Tippy, his actions led to Kipper and his friends being sent to a mental health institute and the police to immediately suspect Mr. Krupp for what happened to the sixth graders (in both the original and changed timeline, Mr. Krupp was unintentionally beaten up by his own nephew, and his friends while escaping from the school due to a blackout). The Cops show up and blame Mr. Krupp. This eventually led to Mr. Krupp being fired which means in a few years he would not be hypnotized by the 3D Hypno Ring into becoming Captain Underpants.

Captain Underpants and the Revolting Revenge of the Radioactive Robo-Boxers
They then go to to to the school with a plan to save the two pets by traveling 65 million years ago and leaving them there. However, Mr. Krupp then notices them and gets mad and furious that the two are running away from him while he is asking them to tell him why they are late to school. It then turns out that he is there with a box of curtains, because they keep on disappearing (due to Captain Underpants using them as capes). When George and Harold reach the library, they lock the door behind them, so Mr. Krupp won't get in. However, Mr. Krupp begins to unlock the door with his keys and barges in after George and Harold who couldn't handle any more problems especially Mr Krupp, they really didn't have the time for him. He then barges in and bangs on the Purple Potty Time Machine demanding that they come out. However, then, Tippy then appears again, and is about to freeze Mr. Krupp. However, when they go back in time, Mr. Krupp also goes with them. (As, he was standing too close to the Purple Potty.) Tippy then sends Tiny Tippy back in time when George and Harold were going in the Purple Potty and Mr. Krupp soon follows. Tiny Tippy then learns that they're going to the Mesozoic era. He then tells his two selves the news, and the three Tippys go back 65 million years.

Meanwhile, 65 million years ago, George and Harold notice that Mr. Krupp is also there with them hanging on a tree branch calling for help. Harold goes out to grab his hand, but then Tippy kicks the tree. The five are then knocked down and the Purple Potty is then destroyed. George, Harold, and Mr. Krupp are saved by Crackers and Sulu. However, Mr. Krupp does not know this yet. Then, Tippy threatens to kill George and Harold. So the boys quickly snap their fingers at Mr. Krupp, turning him into Captain Underpants

later Big Tippy then falls into a lake, turning Captain Underpants back into Mr. Krupp. Just then, Supa Mega Tippy and Slightly Younger Tiny Tippy arrive. Big Tippy then tells the two that Captain Underpants' weakness is water. However then, Supa Mega Tippy then tells Big Tippy that HE is going to destroy Captain Underpants, not him. Out of anger, Big Tippy sets off his nuclear bomb. But Supa Mega Tippy kicks him into another part of the world. However, the bomb still blows up, killing the all the dinosaurs. The six then travel to a time about 200,000 years ago, when cavemen first existed.

Supa Mega Tippy then captures George, Harold, Crackers, and Sulu. Sulu then tears a hole through Super Mega Tippy's robotic hands, and the four friends fly off, promising Mr. Krupp that they'll come back for him. Tippy then holds Mr. Krupp hostage under a waterfall until further notice.

when the ice age starts George, Harold, Crackers, Sulu, and the cavemen run over to Mr. Krupp to free him. However, the ice encases over everyone and freezes them. When all hope seems lost, Slightly Younger Tiny Tippy, now 200 feet tall, grabs everyone with his robotic hands. Then, George and Harold snap their fingers again, turning Mr. Krupp back into Captain Underpants. Atfer Tippy squirts water from the water bottle at Captain Underpants' face, turning him back into Mr. Krupp. While they are all falling, Crackers is getting sicker and sicker for some strange reason. Tippy then captures the five with his hand, and they all get ready to go back home. George and Harold both vow to start acting more mature and take their classes seriously as they go forward in time.

About 200,000 years later, the five notice that they're home. As they are celebrating, they notice that everything looks so old. Then Tippy tells them that he will not hurt them, but is going to destroy Captain Underpants, and that's why he brought them thirty years after the present, so that way the world doesn't have to get destroyed when Captain Underpants is destroyed. He then lets George and Harold go. Crackers is continuing to get sicker, so Sulu makes him a nest. The four friends watch as Tippy tosses Mr. Krupp around with his foot, laughing maniacally.

George and Harold however can't hear the battle due to the yelling teachers nearby. Suddenly, an old Mr. Krupp arrives and tells the teachers to get the students in class now. The duo discover that the screaming and yelling teachers are themselves in the future, but they're not very nice teachers and are actually teachers that are similar to the teachers they are used to. As it turns out, the vow that George and Harold made about promising to act more mature is what made them similar to the teachers they were used to.

In response, the duo make a new vow to always be themselves. After that, the adult George and Harold disappear, leaving old Mr. Krupp standing there confused. Then, they snap their fingers at him, turning him into Captain Underpants. The duo tell old Captain Underpants to save the present Captain Underpants. He does what he is told, and when he brings Mr. Krupp back down, George and Harold snap their fingers, making TWO Captain Underpantses

Captain Underpants and the Tyrannical Retaliation of the Turbo Toilet 2000
After Captain Underpants turns back into Krupp two days later Mr. Krupp is surprisingly happy and claims to the duo it's the greatest day of his life since he met George and Harold. He and Miss Calculator give the duo their report cards and it's revealed that because George and Harold had missed the quizzes, they got bad grades and according to Mr. Krupp, there are no makeup tests for the missed quizzes and the final exams have been canceled this year. However, Mr. Krupp reveals that the worst part for them is that George got 62.7% (which is still passable), but Harold got 59.7% meaning George and Harold will be forced to take different paths after the end of the year.

After George and Harold go to the school However they are seen by the other faculty members and, upon seeing George and Harold in the hallway and their yesterday counterparts in Ms. Ribble's room, they instantly believe they are dreaming and proceed in stripping down to their underwear and doing crazy things. Mr Krupp, however, is shocked by the presence of two Georges and two Harolds in the same way he is in Book 5. saying “B-B-Bubba bobba hob-hobba-hobba wah- wah”. When the police arrive, they arrest the faculty except Mr. Krupp for indecent exposure, reckless endangerment, resisting arrest, and pantsing an officer. The police are unsure of what to do with Mr. Krupp as he didn't actually do anything wrong, but they eventually admit him to the Piqua Valley Home for the Reality-Challenged

Twelve days later, the Turbo Toilet 2000 attacks the city, and George and Harold make Talking Toilet costumes and lure the Turbo Toilet 2000 to break into the Piqua Valley Home for the Reality Challenge (as George and Harold couldn't get pass the woman in the front room to see Mr. Krupp). When the two of them find an intercom after the nurse is distracted off somewhere, a quick finger snap is done through the intercom speakers by the duo in order to for Mr. Krupp to become Captain Underpants then soon after, the Captain is victorious, but one of the Turbo Toilet 2000's tears lands on Captain Underpants' face and he turns back into Mr. Krupp who is then grabbed by the TT2000. Mr. Krupp pleads insanity to the TT2000 to be let go of but TT2000 said he will let him go if he tells him where George and Harold are. So Mr. Krupp directs the Turbo Toilet 2000 to the treehouse of George and Harold, where the Yesterday boys reside. Shortly after he finds the treehouse, the TT2000 breaks his promise of setting Mr. Krupp free and stuffs Mr. Krupp into his stomach swallowing him again like in the second book. The Turbo Toilet 2000 attempts to capture them, but he causes Crackers' eggs to crack and give birth to three strange creatures. At first they take affection to the Yesterday boys, but then they realize that they were in danger. The three hamsterdactyls then attack the Turbo Toilet 2000 and lift him one kilometer above the ground. When the TT 2000 begs to be let go, they do exactly that and drop him, causing him to break apart into many pieces and release Mr. Krupp (who survives due to his super powers). The officers arrive and because Mr. Krupp believes he is having a weird nightmare that he keeps having, they assume that Mr. Krupp is another teacher running around in his underpants that thinks he/she is dreaming, so they arrest him.

Captain Underpants and the Sensational Saga of Sir Stinks-A-Lot
The tiny chunk crashed through the roof of the Piqua Valley Home for the Reality-Challenged, where George and Harold's elementary school teachers are being held.

Ms. Ribble thinks the piece of Zygo-Gogozizzle 24 is a meteorite, and the doctor warns them not to approach it. Unfortunately, Mr. Meaner, the gym teacher, doesn't listen and eats the chunk. He then becomes highly intelligent after the Zygo-Gogozizzle reaches his mind and supercharges all his brain cells. Mr. Meaner then speaks in a standard British accent and decides to leave the insipid infirmary, but the psychologists block the doors. Mr. Meaner immediately comes up with a plan to trick them and tells them they should take his advice not to follow his advice. The two distracted doctors begin to argue if following his advice not to follow his advice is following his advice, Mr. Meaner slips out the open doors. Ms. Ribble notices her chance to escape, and she, along with all the other teachers, dart past the increasingly frustrated and confused doctors.

Outside, the teachers and staff follow Mr. Meaner up to the hilltop and watch in awe as he looks over the horizon, and announces that it occurred to him that all their recent problems were caused by willful and disobedient children. He tells the teachers to follow his every command and to return to school and act normal. School restarts and it appears everything is back to normal and nothing unusual has happened such as crime happening at the school or Mr. Krupp being snapped into a trance becoming Captain Underpants. Everything was just normal but meanwhile overnight Mr. Meaner goes to an old, abandoned factory near Franz Pond and turns it into a makeshift laboratory. Inside, he creates Rid-O-Kid 2000™, a mind-control potion which turns even the most unruly child into a well-behaved child who follows the instructions of adults. He makes it from a base mixture of sodium thiopental containing liberal doses of butyric acid, tryptophan and Clamato juice and filters the solution through a pile of old, dirty gym socks.

The next day, Mr. Meaner arrives at school with two large spray tanks on his back and a metallic belt with buttons around his waist. After gym class, Mr. Meaner excuses all of the children except for Yesterday George and Yesterday Harold. He orders them into his office and locks the door after them. Inside his office, he sprays Yesterday George and Yesterday Harold with Rid-O-Kid 2000™ from the nozzles of his spray tanks. Yesterday George and Yesterday Harold go to their maths class and are well-behaved. Their maths teacher, Miss Calculator, is pleased with their behavior. For the rest of the day, the other teachers notice how well the boys are behaving and after school finishes, they go to all their teachers and collect extra-credit homework.

The following morning at school, Mr. Meaner also has robot arms and hands, having built a giant mechanical ape suit named 'The Stinky-Kong 2000'. He sprays all of the children in his classes with Rid-O-Kid 2000™, giving them all 'Attention Superfluous Lethargy Syndrome (ASLS). Mr. Krupp is delighted that Mr. Meaner has transformed all the children. Ms. Ribble asks if Rid-O-Kid 2000™ is dangerous and Mr. Meaner explains to her that it only affects children and that adults are immune to it.

Later George and Harold dress up as an adult and go to school to find out what's going on. They see all the students acting as slaves for the teachers by doing their work for them, giving them messages, shaving their beards, plucking their eyebrows, giving them haircuts, filling out their tax forms and washing their cars. Harold exclaims that the teachers must have turned all the students into mindless slaves.

The disguised George and Harold then manipulate the children into doing the opposite of what they have been told to do, such as washing the windows wrong, filling their cars with cottage cheese and humiliating the teachers. When the teachers and staff noticed this They along with Mr. Krupp try to find out who is responsible for this but all the children in a trance could tell them that it was a grown up. Mr. Krupp then tells Mr. Meaner about what has happened and this angers him to go out and get to the bottom of whats going on and to find who caused the prank

Later Adult George and Harold rush to Mr. Krupp's house needing help. As they snapped their fingers several times, Mr Krupp however wasn't coming to his trance into becoming his alter ego "Captain Underpants due to his face and head being wet at the time" Mr. Krupp wanted them to go away because to him he assumed they were acting like kids but as this was happening Mr. Meaner overheard what Mr. Krupp said and he grabbed the two adults and he beat them using his ape suit. Mr. Krupp demanded him not to kill them cause he didn't want any blood on his lawn. Adult George and Harold were nearly in a lot of pain but as they finally noticed that Mr. Krupp's Face was dried up and they saw that there could be their final opportunity so they quickly snapped their fingers at Mr. Krupp and he finally came into his trance becoming the amazing Captain Underpants to save his friends.

later Captain Underpants couldn’t save them, as Sir Stinks-A-Lot turns him back into Mr. Krupp with a lot of water, therefore falling down (he was still unharmed because of his superpowers). Sir Stinks-A-Lot then extracts the superpowers as well as the effects from the 3D Hypno Ring ceasing the existence of Captain Underpants from Mr. Krupp. Mr. Krupp (dressed as the fallen hero Captain Underpants) then runs off screaming in terror as Old George and Harold telepathically calls for younger George and Harold

Things were back to the way they were, and as young George and Harold return their older counterparts to their own time, they find that Mr. Krupp didn’t turn into Captain Underpants at the snap of a finger, because Mr. Meaner erased Captain Underpants from existence. As a woman was passing by jogging listening to music and snapping her fingers, Mr. Krupp was still as mean as usual yelling at the woman passing by. George and Harold and their older counterparts decided that they were not going to contribute to the plot and fix the problem which indicated that they were going to move on without Captain Underpants.

The Adventures of Super Diaper Baby
George and Harold were in the gym one day running ketchup packets over with their skateboards on the floor it was all fun and games until their principal Mr. Krupp comes in and yells at them and tells them to clean up the floor and meet him in his office, So George and Harold clean the gym floor up with a garden hose and went to Mr. Krupp's office.

Mr. Krupp is furious with the boys and he punishes them but since writing a sentence over and over on a chalkboard or on paper wouldn't teach the boys anything he assigns them to write a 100-page essay on good citizenship and he angrily tells them not to turn it into a 100-page "Captain Underpants" comic book either. Much to George and Harold's dismay, After they left Mr. Krupp's office. George and Harold were bummed over this assignment until they had an idea they created a new superhero comic called "Super Diaper Baby". The next day they present their 100 page essay to Mr. Krupp which angers him and he sentences George and Harold to detention where they write on the black board.

Super Diaper Baby 2: The Invasion of the Potty Snatchers
The story behind the creation of the original Super Diaper Baby comic by George and Harold is first shown. It is revealed that when their principal, Mr. Krupp, read it, he tore it up, and asked George and Harold why they could never write about anything besides poop. Stumped on what else to write about, George and Harold ask Mr. Krupp. In response to this, he shows them his favorite book when he was their age, "How the Grinch Stole Christmas" by Dr. Seuss. After reading the book, the two friends become inspired and decide not to write about poop. After some careful consideration, they decide to make a sequel to Super Diaper Baby where the main antagonist is made of pee. Thinking Mr. Krupp would be proud of their next epic novel, Mr. Krupp finds it even more offensive than their previous story and becomes furious. In the detention room with busy work yet again, George and Harold say to the reader that as usual, they hope we like it better than Mr. Krupp.

Dog Man: For Whom the Ball Rolls
In the student awards, Mr. Krupp hands out an award for maturity. Melvin thinks it's for him, but Mr. Krupp says it is for George and Harold, since they made a book entitled: Ice Women Diary: A Witch's Tin Key.

Everyone laughs, and Melvin finds out its name is a pun of "I swim in diarrhea, which is stinky." He tells it to Mr. Krupp, and then they both chase George and Harold.

Captain Underpants: The First Epic Movie
Krupp is portrayed in the same way as his book self. However, he is given some sympathetic qualities, while he had very little in the original books. He has a crush on Edith the Lunch Lady (who, as well, has a crush on him).

The Epic Tales of Captain Underpants
Mr. Krupp is now portrayed as incredibly stupid and mean. He has also developed a love for guacamole and salami, though he developed salami intolerance due to eating it too fast. Krupp's shown to be not very bright, even as a principal, and has always been a bully. However, there are still times where he is somewhat decent, though it's usually because it would benefit him, such as when he allowed the students and faculty of Jerome Horwitz Elementary School to go to space so he could have a chance to outshine his high school rival.

In "The Soggy Salvation of the Swirling Sweatnami," it is revealed his childhood was terrible. His mother, Bernice Krupp, verbally abused him and only saw him as a disappointment. When Mr. Krupp entered the school talent show and tried to perform as a rapper, Bernice humiliated him and encouraged his peers to do the same. This incident led Benjamin to become the spiteful principal he is today.

As a teenager, he was under the impression he competed with Moxie Swaggerman, despite her barely being aware of his existence. When Mr. Krupp meets Moxie again in The Epic Tales of Captain Underpants in Space!, he attempts to serve as the schoolship's leader but fails horribly, even sending the School Spaceship to a planet called Utopiqua.

Whenever he transforms back from Captain Underpants, he doesn't seem to know why he is in his underwear after being soaked in water.

Trivia

 * Benjamin's nickname, Benny Krupp, is a pun on "bank-krupp"
 * Benjamin's last name was supposed to be Crutch, as a reference to the character of the same name from the 1934 Our Gang/Little Rascals short film "Shrimps for a Day", but Pilkey remembered it incorrectly. If Pilkey's memory had been better, then Mr. Krupp would've been called Mr. Crutch.
 * As revealed in Captain Underpants and the Wrath of the Wicked Wedgie Woman, Benjamin is Jewish, and most likely a Reform Jew. Strangely enough, this trait isn't acknowledged at all in The Xtreme Xploits of the Xplosive Xmas.
 * In the first book, he hates the Captain Underpants comic books that George and Harold make. Ironically, he would later become Captain Underpants himself.
 * He, Captain Underpants, George, and Harold are the only characters to appear in every episode of The Epic Tales of Captain Underpants.
 * Even though he is unaware that he is Captain Underpants, there are several times where he is doused with water in the middle of the battle with an enemy. When this happens, Benjamin is angry and confused as to what is happening, where he is, and why is he wearing his own curtains around his neck and in his underwear in public.
 * Dav revealed that Benjamin's birthday is April 1st, which is April Fools Day (the same birthday as Professor Poopypants), and that he is in his mid-forties.
 * In the film, he is given a love interest in the form of Edith the Lunch Lady.
 * In the film, the gold plate on the front of his desk was changed from "Kneel Here" to "Hope Dies Here". Though, some of the early film promotional pictures had "Kneel Here" on it (or the plate was blank).
 * In the film, while George and Harold bring him home as he is knocked out on a wagon, they start to plunder in his home but find nothing interesting. On the outside, signs say "Keep out", "Danger", or "Go away". No one lives in the house but him.
 * It is revealed that Krupp is lonely at heart and lives in an empty home with no one to care about him. His mattress has an imprint of his body where he normally sleeps, he has only one fork in the drawer, a towel with the words "His" and the other towel "Still His", and only one box of "Not So Cheerios" cereal box left on his cupboard in the kitchen, the dining table has only one plate and glass placed there.
 * Towards the end of the film, he realizes that George and Harold's Captain Underpants comics are humorous and funny. He has a slight change of heart about the boys since they (unknown by Krupp) help him and Edith get together on a date.
 * He has accidentally snapped himself into becoming Captain Underpants thrice. Once in Book 5, Another in The Heartbreaking Havoc of the Haunting Hack-A-Ween and another time at the end of the film.
 * Although, it may be possible he put two and two together and snapped on purpose.
 * Mr. Krupp only reforms in the film; he never redeems himself in the book series and TV show. In an interview, Dav Pilkey said he was happy with the film giving Krupp actual character development, a backstory, and redemption arc; to the point where Dav wished he did the same in the books.
 * It is possible that this is the reason why he had Petey reform in the Dog Man series.
 * Mr. Krupp had a habit of making up rules and scribbling them in the rulebook, which got him fired in the show. When Melvinborg expelled George and Harold for breaking the rules in that same book, he got struck by bureaucracy, as the rules that were broken were unofficial, and therefore they did nothing wrong.
 * In Captain Underpants: The First Epic Movie, Mr. Krupp's tie is brown, and he wears green pants. Also, his white shirt has a pocket. In The Epic Tales of Captain Underpants, he wears a purple tie and brown pants. There's also no pocket on his white shirt.
 * In the TV show, Mr Krupp overeats avocado, guacamole, and salami.
 * He says “B-B-Bubba bobba hob-hobba-hobba wah- wah” when he doesn't know what to say.