Captain Underpants and the Perilous Plot of Professor Poopypants

A scientist from the country of New Swissland (a country that doesn't exist, with a foreign culture where everyone has a silly name) called Professor Pippy P. Poopypants goes to the United States to demonstrate how his striking Shrinky-Pig and Goosy-Grow can help the world by reducing the garbage and increasing food, but everyone laughs at Poopypants' name rather than take him seriously.

Meanwhile, Jerome Horwitz Elementary School is going to a restaurant-arcade called The Piqua Pizza Palace, but when George and Harold rearrange the sign, Mr. Krupp catches the boys as he bans them from the school field trip and demands they clean the teachers' lounge, making them lose their chance of going to the Piqua Pizza Palace with everyone else. However, the boys get their revenge by modifying things around in the teachers' lounge and after the field trip, the teachers fall into George and Harold's trap and get largely covered in glue and foam pellets. They chase the boys around the school and after seeing the teachers looking like abominable snowmen, Mr. Fyde quits, thinking he's losing his sanity, prompting Mr. Krupp to find a new science teacher.

Meanwhile, Professor Poopypants sees an ad to teach at the school and applies for the job, thinking children to be kind and sweet-hearted, but they spend days laughing at his silly name. The professor only gets them interested by building a robot that makes gerbils jog along with them but it is short-lived. Some time later, Ms. Ribble reads The Pied Piper of Hamelin, which inspires George and Harold to make a comic about the Professor trying to take over the world, which destroys the last of Professor Poopypants' sanity.

He makes the gerbil machine as large as a tall building, then shrinks the school and holds them hostage to turn their names sillier, with a system of three alphabetical name charts based on the first/last letter of each part of a first and last name. George and Harold (now Fluffy and Cheeseball) get Captain Underpants (now Buttercup Chickenfanny, but refuses to take the professor's order to change names) to steal Professor Poopypants' enlarging machine, but he and the machine are shrunk in the process. The two of them try to enlarge the school back to normal size, but get flicked off the school. Cheeseball makes a paper airplane that Fluffy enlarges and after many dangers, Underpants rescues them. Fluffy enlarges Underpants to the gerbil's size, then he defeats Professor Poopypants and everyone's names revert. The boys use the machines to bring themselves, the school and Captain Underpants back to normal size. Captain Underpants is soaked with water, turning him back into Mr. Krupp.

Professor Poopypants is hauled off to jail for crimes against humanity. From the advice of George and Harold, he legally changes his name so that no one will make fun of it anymore. Unfortunately, he changes his name to his grandfather's, Tippy Tinkletrousers, that which only makes the prisoners (and police officers) laugh at him even more, much to his anger.

• George Beard/Fluffy Toiletnose
• Harold Hutchins/Cheeseball Wafflefanny
• Mr. Benjamin Krupp/Mr. Lumpy Pottybiscuits
• Captain Underpants/Buttercup Chickenfanny (he did not change his name, because he does not take orders from anybody)
• Chuckles Jingleberry McMonkeyburger, Jr.
• Stinky McMonkeyburger
• Jiggles T. Chunkyskunks
• Tipper Q. Zipperdripper
• Professor Pippy P. Poopypants/Tippy Tinkletrousers
• Porkbelly Funkyskunk
• Connor Mancini/Buttercup Bananalips
• Aaron Mancini/Stinky Bananalips
• Ingrid Ashley/Chim-Chim Diaperbrains
• Larry Zarrow/Booger Stinkersquirt
• Stephanie Yarkoff/Snotty Gorillabreath
• Robbie Staenberg/Loopy Pizzapants
• Janet Warwick/Poopsie Chucklebutt
• Melvin Sneedly/Pinky Pizzabrains
• Ivana Godadebafroom/Chim-Chim Lizardtushie
• Mr. Rected/Mr. Gizzardnose
• Miss Labler (mentioned)/ Miss Liverbuns (mentioned)
• Ms. Tara Ribble/Ms. Falafel Gizzardtush
• Mr. Kenny B. Meaner/Mr. Flunky Bananabuns
• Miss Edith Anthrope/Miss Crusty Diapertush
• Ms. Guided/ Ms. Lizardnose
• Mr. Morty Fyde/Mr. Pinky Barftush
• Dr. Diaper (cameo)/ Dr. Bubblebuns (cameo)

Authors:

• Cynthia Rylant/Buttercup Gizzardsniffer
• Dav Pilkey/Gidget Hamsterbrains
• Dan Santat/Gidget Pizzasniffer
• Jose Garibaldi/Poopsie Lizardlips
• Martin Ontiveros/Pinky Burgerfanny

• Dav Pilkey
• Captain Underpants

The book that followed this was The Wicked Wedgie Woman (2001).

The Book received mainly positive reviews from critics.

The main antagonist of the book, Professor Poopypants, would return in later books of the series as both a recurring character and even the main villain. He would also return in Captain Underpants: The First Epic Movie.

The book was removed from an elementary school in Page, North Dakota due to parental complaints.[1]