Chapter 1: George and HaroldWe meet George, the kid with the tie and flat-top, and Harold, the kid with the t-shirt and the bad haircut (Remember that now.) and witness their lovable prankster nature as they change a sign from "Pick your own roses" to "Pick our noses!" We are told that they are best friends, next-door neighbors, and attend the same class together at Jerome Horwitz Elementary, and that they're good boys, if not necessarily sweet and lovable. Their silly streak, however, can get them into big trouble... and it does.
Chapter 2: Tree House Comix, Inc.George and Harold's tree house based production company, Tree House Comix, Inc, is where George writes and Harold draws their collaborative comics, including Dog Man, Timmy the Talking Toilet, the Amazing Cow Lady, and especially their greatest creation, the Amazing Captain Underpants! (Created when George decided to make the concept of super heroes in their underwear literal.) The two use the school copier to print them, and run a brisk business selling copies at fifty cents a piece.
Chapter 3: The Adventures of Captain UnderpantsAll your favorite superheroes are too old to fight crime, but not the Amazing Captain Underpants! At an elementary school, he fights the Inedible Hunk, an animate disgusting cafeteria food, by flushing it down a toilet.
Chapter 4: Mean Old Mr. KruppWe're introduced to Mr. Krupp, the child-hating principal of Jerome Horwitz, who hates George and Harold most of all and vows to get them one day very, very soon.
Chapter 5: One Day Very, Very SoonThe boys put pepper into the cheerleaders pompoms, bubblebath in the band members instruments, helium in the football, replace the football players muscle cream with itching cream, and much more, ruining the big game for everyone. They don't let up with the pranks, rendering the entire school miserable, save them. Harold is worried that they'll get busted. George reassures him that they won't.
Chapter 6: BustedThe next day, the boys were proven wrong. Confronted in the Principal's office by an evilly grinning Mr. Krupp, the dastardly principal presents them with incontrovertible evidence of their escapades: a videotape!
Chapter 7: A Little BlackmailMister Krupp gleefully muses over what to do with the tape: Send it to their parents? The school board? No... the football team! George and Harold beg for mercy, and Krupp grants it, on several draconian conditions...
Chapter 8: Crime and PunishmentThe boys do chores for Mister Krupp, abide by his rules, and cater to his every whim, getting extra homework in the evening. George gets an idea to order a hypno-ring and hypnotize Mr. Krupp into giving them the tape.
Chapter 9: Four-to-Six Weeks LaterThe 3-d hypno-ring arrives! George and Harold admire it.
Chapter 10: The 3-D Hypno-RingThe two boys bring the hypnoring to school, shirking Mr. Krupp's demands, and angering Mr. Krupp to no end. He's not angry for long, as the two hypnotize Mr. Krupp with the ring and a snap of their fingers. They swap out the tape with a kids sing-along video.
Chapter 11: Fun with HypnosisGeorge and Harold find all of their old Captain Underpants comic books in the process of rummaging through Mr. Krupp's file cabinet. After spending the rest of the morning reading the comics, they hypnotize Mr. Krupp into becoming a chicken, a monkey, and finally, since he does own every issue, The Amazing Captain Underpants. With a tra-la-la, Mister Krupp becomes Captain Underpants, and the boys laugh so hard, they don't notice him leaping out the window.
Chapter 12: Out the WindowThe boys spot Captain Underpants cutting across the school lawn, and rush after him on their skateboards (but not before retrieving some slingshots and fake doggy-doo from Krupp's file cabinet).
Chapter 13: Bank RobbersThey finally find Captain Underpants in the midst of waylaying some bank-robbers, by making them laugh themselves silly over his ridiculous appearance. The cops who arrest them also try to arrest Captain Underpants, but George and Harold whisk him away on their skateboards.
Chapter 14: The Big BangWhile stopping to rest, they are knocked off their feet by an explosion coming from the Rare Crystal shop, which robots are robbing!
- George: You know, up until now this story was almost believable!
Chapter 15: Dr. DiaperDr. Diaper, unaware of the boys, has tied up Captain Underpants and explains his plan to destroy the world with a crystal powered laser. George distracts him with the doggy-doo, and...
Chapter 16: The Extremely Graphic Violence Chapter...through the cheesy animation technique of Flip-O-Rama, the boys destroy the two robots guarding the Captain.
Chapter 17: The EscapeGeorge and Harold untie the captain and trigger the Laser's self-destruct, but Dr. Diaper has them at ray-gun point! The Captain fires his under wear like a slingshot into Dr. Diaper's face, and our three heroes escape the warehouse, Dr. Diaper in tow, just as the Laser causes a massive explosion. Are they doomed?
Chapter 18: To Make a Long Story Short
They got away.
— The Adventures of Captain Underpants