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Captain Underpants and the Perilous Plot of Professor Poopypants is the fourth book in the Captain Underpants series written by Dav Pilkey. It is the first book where Captain Underpants fully uses his superpowers.

This book is dedicated to fellow children's book writer Cynthia Rylant. (Buttercup Gizzardsniffer)


Tra-la-laaa!! The New York Times and USA Today bestselling Captain Underpants series is now available in eBook edition, featuring Flip-O-Rama, bonus content, and more! George and Harold aren't bad kids. They just like to "liven things up" for everybody. Unfortunately, their THOUGHTFUL jokes sometimes get them into a LOT of trouble. And when Professor Pippy P. Poopypants becomes their new science teacher ... well, George and Harold almost cause the entire planet to be taken over by a maniacal, mad-scientist guy in a giant robot suit! Who will stop the perilous plot of Poopypants?!!? This looks like a job for Captain Underpants!

Source: Publisher


Professor Poopypants, a scientist from a country where everyone has a silly name, New Swissland, has just invented a shrinking machine, the Shrinky-Pig 2000 and an enlarging machine, the Goosy-Grow 4000. He goes to America so he can show these inventions to everyone and help the world by using his machines to shrink the world's garbage and increase the world's food supply.

Meanwhile, 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 have 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 activate it when the water runs, second they put powdered paste on the ceiling fan blades as well as altering the light switch so the fan would turn on when the lights go on. 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 water nozzle sprays the teachers soaking wet as the fan spreads the powdered paste onto the teachers. Finally, when the fridge door opens up, the foam pellets fly everywhere due to the fan, and land on the teachers. 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 out 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.

Meanwhile, Professor Poopypants has been trying to demonstrate his new inventions to the world, but nobody takes him seriously, due to laughing at his silly name. Eventually he begins running out of money to become a teacher at a school. He then goes to a New York coffee shop and after finding an ad, he decides to become an elementary school science teacher. During this time, the boy who sees everything his mother can't is seen pouring salt into Professor Poopypants's coffee. He is convinced that the innocence and sweetness of children will let them pay attention to him, but they all laugh at his name instead after he declares what it is.

A week later, Professor Poopypants manages to get the children interested in science by building a machine called the Gerbil-Jogger 2000 that allows gerbils to jog alongside their masters. However, this interest is short-lived (thanks to George), as he reveals his middle name to be Pee-Pee, causing the children to start laughing again. Later in English, Ms. Ribble reads the story of The Pied Piper from Hamelin. This inspires George and Harold to make a Captain Underpants comic book about the Professor inventing an army of gerbil joggers to destroy the world using a pair of headphones on the gerbils to control them and everyone in the comic, including Captain Underpants who laughs at his name, which 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 (as revenge for everyone making fun of his name). 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.

As bad as the situation was getting, George and Harold (now Fluffy and Cheeseball) have no choice but to get Captain Underpants's help knowing that they would regret it. So they rush to Lumpy Pottybiscuits's (Mr. Krupp) office where he is seen under his desk cowardly hiding in fear of Professor Poopypants. Fluffy snaps his fingers at him and he becomes Captain Underpants (now Buttercup Chickenfanny, but Captain Underpants refuses to change his name) to steal Professor Poopypants' enlarging machine, but unfortunately he gets caught and both him and the machine are shrunk in the process. The enlarging Machine makes its way to Fluffy and Cheeseball but Captain Underpants wasn't seen bringing it to them.

While Captain Underpants's presence is unknown, Fluffy and Cheeseball try to enlarge the school back to normal size by getting onto the roof, but they get flicked off the school by the Professor as they are falling to their deaths. Cheeseball quickly makes a paper airplane that Fluffy enlarges. The plane flies into many threats, yet tiny Captain Underpants rescues them and they end up in an abandoned alley. Captain Underpants was also the one steering the plane out of danger they assumed.

Fluffy tries to enlarge Captain Underpants, but he accidentally enlarges Cheeseball's right hand in the process, however Captain Underpants does become visible, George zaps C.U. until he is the size of Professor Poopypants' gerbil machine. Captain Underpants then fights and defeats Professor Poopypants. 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.

Before Professor Poopypants is then hauled off to jail. George then questions Professor Poopypants wouldn't it have been smarter to try changing his own name instead of forcing the rest of the world to change theirs. The surprised professor notes he never thought of that. As per George's advice, Professor Poopypants changes his name so no one will make fun of it anymore. (The letter indicates Professor Poopypants said he is sorry for being evil, but in his next appearances, he became evil again). Sadly, he chooses his grandfather's name (on his mother's side), Tippy Tinkletrousers, which Dr. Diaper and the inmates at the jail facility make fun of him (including the guards).

Meanwhile, while at the Treehouse in the backyard of their homes, Harold tells George that he learned something today. The moral of the story ("I think this is the first time one of our stories had a moral," notes George) is that it's not nice to make fun of people.

George and Harold unfortunately forgot another moral in the story which was: Do not hypnotize the school principal, because anything can go from bad to worse at the snap of a finger. Mr. Krupp then turns back into Captain Underpants (thanks to Ms. Anthrope) with George and Harold holding onto his cape saying, "Oh No!" and "Here we go again!", as Captain Underpants flies out the school, singing his battle cry happily.




  • In the original printing of the book, there is an apology and a giveaway at the end of the book, aimed at people who were "traumatized" by the new names inflicted on them by Professor Poopypants.
  • In the color hardcover version of this book, there are five bonus fun facts at the end and an introduction to an upcoming comic created by George and Harold.
  • Professor Poopypants is loosely modeled on Albert Einstein, despite a large height difference.
  • In the Spanish version of this book, the gerbils listen to music by Julio Iglesias.
  • The two news reporters, Ingrid Ashley and Larry Zarrow, appeared in the fifth novel as well. They still used the names that Professor Poopypants made for them in this book, possibly because they are getting used to it.
  • The tape on the water sprayer nozzle prank, was a prank Dav himself did as a child.
  • On the inside of the cover it shows Professor Poopypants crossing out Dav Pilkey's name and writing the silly equivalent (Gidget Hamsterbrains).
  • Near the end, Dr. Diaper makes a cameo appearance in the jail where the professor is sent to at the very end of the book. He, along with many others in the jail, are seen laughing at Professor Poopypants's unbearably funny new name.
  • This book marks the first time that Mr. Krupp and Mr. Fyde's first names are mentioned, which are Benny and Morty respectively.
  • The small print newspaper Professor Poopypants reads contains an article about robots and toilets on Uranus (a reference to the second book), and an article about how reading small print is bad for people's eyes, which is probably telling the reader not to read the newspaper on the page, or it's just a bit of irony put in by Dav Pilkey.
  • The small print statement was stated to be written by Dr. Kent C. Toogood, a scientist from Maggoo University. This scientist's name is a pun on the word 'I can't see too good', while Maggoo University is named after Mr. Magoo, a cartoon character with famously poor eyesight.
  • In the original edition of this book, the logo for Piqua State Penitentiary seen in the letter on page 145 contained an error. The abbreviation Penn. is used. Dav claims this was not his fault.
  • In reference to their names, the Shrinky-Pig 2000 looks like a pig (a farm animal) and the Goosy-Grow 4000 resembles a goose (a type of bird).
  • When Professor Poopypants is extolling the kindness and innocence of children, a boy can be seen, ironically, pouring salt into his tea.
  • When the teachers (covered with packing peanuts) chased George and Harold, Morty Fyde could be seen on the other side of the window. Fyde later hands in his resignation, stating facts that involved George and Harold's odd experiences that he believed himself to have imagined.
  • Professor Poopypants has been literally laughed out of several famous colleges when he tried to present the Goosy-Grow and the Shrinky-Pig (some of those colleges include Harvard, Georgetown, Yale, Stanford, and Chattanooga State Tech Community College).
  • A student named Robbie Staenburg is mentioned as a student whose name was changed; Robbie Staenburg is the son of Dav Pilkey's agent.
  • When Professor Poopypants gets in the big Gerbil Jogger, he is bigger than he was before.
  • Connor Mancini is the name of Dav Pilkey's nephew.
  • This is the first time George is shown alone.
  • This is the first book where the cover shows Captain Underpants with his mouth open, which is how it is for all books, starting with this one.
  • This is the only book where a character says a religious exclamation. In this case in the last page of the comic book that Professor Poopypants was holding, one of the children is shown saying, "Please God! Make it stop!".
  • Chapter Thirteen's name is a parody of the movie "Honey, I Shrunk the Kids".
  • Professor Poopypants' new name, Tippy Tinkletrousers is, according to the letter he wrote at the end, his grandfather's name on his mother's side.
  • The kid and his mother from the first and second book appear twice in this book.
  • Oscar Myers from Hallow-Wiener (one of Dav's picture book characters) makes a special guest appearance in this book on pages 107 and 108 (105 and 106 in the full color edition) as the dog who tries to bite George and Harold.
  • This is the first color edition book to exclude the bubbles on the cover.
  • In printings up to 2016, In the info page, it says "For Buttercup Gizzardsniffer with love". Nowadays that is removed and replaced by an image of Professor Pippy Pee-Pee Poopypants.
  • Chapter 18's name is a parody of "Are You There God? It's Me Margaret." By Judy Blume.
  • This is the last color edition book to have the fun facts at the end.

New Names[]

Inventions Used[]


See Also[]

Main Books in Main Series
Captain Underpants
The Adventures of Captain UnderpantsCaptain Underpants and the Attack of the Talking ToiletsCaptain Underpants and the Invasion of the Incredibly Naughty Cafeteria Ladies from Outer Space (and the Subsequent Assault of the Equally Evil Lunchroom Zombie Nerds)Captain Underpants And The Perilous Plot of Professor PoopypantsCaptain Underpants and the Wrath of the Wicked Wedgie Woman • Captain Underpants and the Big Bad Battle of the Bionic Booger Boy ( Part 1) ( Part 2) • Captain Underpants and the Preposterous Plight of the Purple Potty PeopleCaptain Underpants and the Terrifying Return of Tippy TinkletrousersCaptain Underpants and the Revolting Revenge of the Radioactive Robo-BoxersCaptain Underpants and the Tyrannical Retaliation of the Turbo Toilet 2000Captain Underpants and the Sensational Saga of Sir Stinks-A-Lot
Super Diaper Baby
The Adventures of Super Diaper BabySuper Diaper Baby 2: Invasion of the Potty SnatchersSuper Diaper Baby 2½Super Diaper Baby 3: Petey’s Revenge
Ook and Gluk
The Adventures of Ook and Gluk: Kung-Fu Cavemen From the FutureThe Adventures of Ook and Gluk Jr.: Kung-Fu Cavekids in Outer Space
Dog Man
Dog ManDog Man: UnleashedDog Man: A Tale of Two KittiesDog Man and Cat KidDog Man: Lord of the FLEASDog Man: Brawl of the WildDog Man: For Whom the Ball RollsDog Man: Fetch-22Dog Man: Grime and PunishmentDog Man: Mothering HeightsDog Man: Twenty Thousand Fleas Under the SeaDog Man: The Scarlet ShedderDog Man: Big Jim Begins
Cat Kid Comic Club
Cat Kid Comic ClubCat Kid Comic Club: PerspectivesCat Kid Comic Club: On PurposeCat Kid Comic Club: CollaborationsCat Kid Comic Club: Influencers