Captain Underpants and the Revolting Revenge of the Radioactive Robo-Boxers

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Book Number
Release Date
January 15, 2013
Number of Pages
Preceded by
Succeeded by

Captain Underpants and the Revolting Revenge of the Radioactive Robo-Boxersis the 10th book of the Captain Underpants saga. It was released by Scholastic Inc. on January 15, 2013.



The book picks off where the last one left off, where Tippy was crushed by the zombie nerd from Book 9. However, after an explanation on how elephants are slow due to their heaviness even if they are shrunk, it is revealed that Tippy wasn't really squashed, because giant evil zombie nerds are incredibly slow. So, Tippy goes off to a convenience store and buys a cherry cough drop and a new bow-tie. Then, Tippy notices an extra-large ketchup packet and buys that too. Tippy saves himself with the ketchup packet.

He then travels four years ago and freezes Kipper, Bugg, Finkstein , and Loogie who were running out the school going crazy from the young George and young Harold's first successful prank. Tippy freezes them from running further before his Tippy's Slightly Younger version arrives to accidentally scare them. When Slightly Younger Tippy does arrive, Future Tippy tells him that he is there to stop him from scaring the bullies. Then, he shrinks Slightly Younger Tippy and travels four years into the future. The bullies unfreeze and continue running as they were. Arriving in the present, Tippy sees that the timeline is back to normal, however he has also arrived at the point where George and Harold were getting arrested in Book 8. He then freezes the cops, and chases George, Harold, Crackers, and Sulu around town. The next day, George and Harold are still hiding from Tippy's robotic freezing pants.

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 his alter ego 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.

As Tippy chases the five, Tiny Tippy and Slightly Younger Tiny Tippy TinkletrousersTiny Tippy become tired of letting regular Tippy boss them around, so they go back in time to chapter 8 of book 9 to get the Goosy-Grow 4000 from the top half of their suit so that way they can grow bigger than big Tippy. Slightly Younger Tiny Tippy then zaps Tiny Tippy and turns him into Supa-Mega Tippy TinkletrousersThen, Supa Mega Tippy betrays Slightly Younger Tiny Tippy, who climbs onto his suit as a stowaway. He then goes back 65 million years ago when Big Tippy captures Captain Underpants, who up until then thought that they were playing chase.

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. 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 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.

Meanwhile, the four friends travel over to a cavepeople village, asking for help. However, they don't understand their accent. Tippy then attacks the village, forcing them all to seek refuge in a cave. George and Harold discover that the cavepeople understand pictures better, so they write a wordless comic book on the cavewalls to help the cavepeople that Tippy is evil and he must be stopped.

After the cavepeople finish reading the comic, they and the duo all start drawing out plans on how to stop Tippy. They then set up traps for Tippy and even burn up his robot pants. And when he fires the Freezy-Beam 4000 at the cavemen, Slightly Younger Tiny Tippy tampers with it so it won't turn off. Tippy tries his hardest to turn it off, but the emergency shut off is stuck. The ice spreads throughout the destroyed village quick, and into the mountains. Slightly Younger Tiny Tippy then steals the Goosy-Grow 4000, and zaps himself to a range of 120-150 feet. As he is about to reach 200 feet, the Goosy-Grow 4000 then falls on the ice, spreading it throughout the world.

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, 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. Captain Underpants rips off Tippy's robotic pants, leaving him standing there in his boxers.

Using the pants as a net, Captain Underpants, George, Harold, Crackers, and Sulu take to cave people over to France, giving them a new place to live. When they return to Tippy, asking for a ride back to the future, 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. They each beat up Tippy and his giant robo-boxers, but Tippy then sets off his nuclear bomb. Tippy then states to the six that the bomb will destroy the entire galaxy, as it is more powerful then a supernova. Suddenly, Crackers and Sulu sacrifice themselves by sending themselves, Tippy and the Robo-Boxers back 13.7 billion years ago. When the three go back, the bomb explodes, causing the Big Ka-Bloosh theory, incinerating Tippy and creating the universe.

13.7 billion years later, George, Harold command old Captain Underpants to gather his clothes, fly into the school, get dresses and wash his face off with water to turn back into old Mr. Krupp. They along with Present Captain Underpants realized that they are stuck in the future without a time machine. Then, Harold points out that Crackers is a girl, because she laid three eggs. The three then decide to take care of the eggs, seeing as Crackers did something for them, so in return, they'll do something for HER. As the three are walking through town possibly going to see if their homes are still around they could stay in, Melvin appears in an octopus suit and grabs Captain Underpants and the boys. They thought they was going to be in danger by Melvin again but Melvin takes them back to the present time from which they left in the first place in Melvin's last invention "The Purple Potty Time Machine", Melvin warns them that something bad has happened since they've been gone.


Main Characters


Other Characters

  • Cavemen
  • Children


  • 13.7 billion years ago (...)
  • 65 million years ago (...)
  • 200,000 years ago (...)
  • 5 years ago (2007)
  • 10 minutes ago (...)
  • Present (2013)
  • 30 years in the future (2043)

Compared Events of time in Reality & the CU universe

Reality CU Universe
The universe began when a major atom formation that appeared then exploded 13.7 billion years ago Crackers, Sulu & Slightly Younger Tiny Tippy went back 13.7 billion years ago, where then a giant Thermoulnuclear bomb exploded, thus originating their universe!
The dinosaurs got killed when an asteroid that simotainsly fell from space hit the earth in Arizona 65 million years ago Supa Mega Tippy Kicked Big Tippy over into the Gulf of Mexico, where his bomb exploded at massive force precisely 65 million years ago
Art was started by the previous evolution period before Homosapians & became a natural thing of man since George & Harold showed early man how art was done, especially how to defeat Tippy
Harsh weather patterns 200,000 years ago set climates at a freezing standing, thus beginning the last major ice age in north America Tippy's parodoxes sabotaged his Freezy-Beam 4000 which then rapidly froze the area around, then expanded when the Goosy-Grow 4000 aimed directly below.
Mans nationalities formed in different kinds as they migrated and settled in different continents Almost every sub-race of humanity delled in the Americas, Until the ice age came by, thus they moved to Afro-Eurasia, to a cave in southern France.


  • This is the final appearance of Sulu and Crackers as they sacrificed themselves to stop Tippy Tinkletrousers from using his bomb to destroy George, Harold, and Captain Underpants. It is also the final appearance of Tippy Tinkletrousers as he is killed by his own bomb.
    • This is also the first time good characters have been killed off in the series.
  • Crackers is confirmed to be female in this book as she laid three eggs before she and Sulu sacrificed themselves.
  • Despite what the 9th book said, this is not the final book of the Captain Underpants series. Dav Pilkey stated on his website that he had intended for this book to be the final Captain Underpants book. However, he felt that there were too many loose ends and created the eleventh book to try and tie them all up.
    • Despite this, the eleventh book also got too many loose ends as well.
  • This book shows three predestination paradoxes as Tippy was responsible for the extinction of the dinosaurs, the Ice Age, and the creation of the universe. Another predestination paradox was George and Harold creating the first cave drawings.
  • Melvin Sneedly makes a cameo for this book, and will appear in book 11, possibly having a major role.
  • This book is the second longest story in the series by far, having 224 pages. The longest being book 9, with 304 pages.
  • This book confirms that George and Harold will become similar to the teachers they are used to if they ever vow to change their ways.
  • This is the first book where there is no sign changing by George and/or Harold due to them being stuck in the Mesozoic era and the Ice Age for a majority of the book.
  • In the chapter: Let's get serious folks!, some kids in the classroom are pretending to not enjoy reading the book, a girl in the middle bottom of the second page is flipping a Flip-O-Rama section that resembles a section in the book.
  • Goof: Tippy had his Shrinky Pig 2000, and Goosy Grow 4000 in his Robo-Suit, however it is shown in the fourth book and eighth book that they went into George and Harold's possession after Tippy was arrested in the fourth book. Though it could be possible that Tippy had made copies of them back in the fourth book.
  • Goof: In chapter 8, the two Tiny Tippys go back to when Captain Underpants was battling Tippy in book 9. However, this is a flaw because in the start of this book Tippy prevented that battle from preventing, therefore, the top half of the suit never existed.
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