All spoilers are unmarked!
Season 1
- "Captain Underpants and the Frenzied Farts of Flabby Flabulous": George and Harold get revenge on their gym teacher by writing him into a ridiculous new comic. But the joke's on them when life imitates art.
- "Captain Underpants and the Dreadful Debacle of DJ Drowsy Drawers": A school dance sounds like fun — but only if the boys can keep their music teacher from playing DJ and putting everyone to sleep.
- "Captain Underpants and the Horrible Hostilities of the Homework Hydra": To get out of an epic assignment, George and Harold go back in time to the moment homework was invented to try and stop it before it starts.
- "Captain Underpants and the Vexing Villiany of the Vile Vimpire": After Erica critiques their comic book, George and Harold create a brand-new character — a vampire who sucks the joy out of everything.
- Captain Underpants and the Terrifying Perilous Misfortune of the T.P. Mummy": A T.P. prank gone wrong leads to clogged toilets — and a fateful explosion — that turns the boys' new French teacher into a mummy.
- "Captain Underpants and the Squishy Predicament of the Stanley Peet's Stinky Pits": Holy guacamole! George and Harold are so determined to win an avocado-growing contest that they accidentally turn their science teacher into a monster.
- "Captain Underpants and the Costly Conundrum of the Calamitous Claylossus": Rumors swirl around the shadowy Bo Hweemuth, a mysterious student with secret gifts who has the whole school living in fear.
- "Captain Underpants and the Jarring Jerkiness of the Judge J.O.R.T.S.": The boys' latest comic inspires their jorts-wearing Spanish teacher to become a superhero with otherworldly powers.
- "Captain Underpants and the Strange Strife of the Smelly Socktopus": After Erica compares her suspension to a vacation, a jealous George and Harold pull every prank in the book so they can get suspended, too.
- "Captain Underpants and the Flustering Mindless Woe of the Flushable Memory Wipes": A chocolate-pudding "incident" sends George and Harold into hiding. But there's a new principal when they come back — and no one remembers them!
- "Captain Underpants and the Soggy Salvation of the Swirling Sweatnami": The boys travel back in time to stop Mr. Krupp from becoming a bully, only to find that their plan has turned him into a ruthless businessman.
- "Captain Underpants and the Sickening Fumes of Smartsy Fartsy": To steal Mr. Krupp's rule book from a tightly locked safe, the boys cook up a super-intelligent gas cloud who winds up turning against them.
- "Captain Underpants and the Troublesome Treachery of the Thieving Toot Fairy": It's a race against time as George and Harold try to get Mr. Krupp fired before he can have them expelled. But first: a faceoff with the Toot Fairy!
Season 2
- "Captain Underpants and the Tenuous Takedown of the Tyrannical Teachertrons": With Mr. Krupp gone and two terrible Melvins in charge, George and Harold fight back by hypnotizing their gym teacher, Mr. Meaner.
- "Captain Underpants and the Frantic Fury of the Fearsome Furcules": The boys recruit kids to join the M.I.S.F.A.R.T.S.— the Mega Incredible Search Force Adventure Rescue Team Squad — and bring Mr. Krupp back to school.
- "Captain Underpants and the Harmful Horrors of the Harrowing Hiveschool": After injecting all the teachers with bee DNA, the Melvins run the new “hive mind” of the school — until Ms. Ribble accidentally becomes queen bee.
- "Captain Underpants and the Preposterous Pulverizing of the Pestering Poopacabra": George and Harold train a rat for extra credit. But when their subject escapes into the sewers, he’s doused with toxic waste and becomes… Poopacabra!
- "Captain Underpants and the Dastardly Deed of the Devious Diddlysaurus": Who knew a thawed-out dinosaur could read comics and pull pranks? Well, this one does — and he’s one of George and Harold’s biggest fans.
- "Captain Underpants and the Shadowy Syndrome of the Sinister Splotch": Captain Underpants becomes a wanted man when a criminal who looks just like him starts robbing banks. Can George and Harold help clear his name?
- "Captain Underpants and the Bizarre Blitzkrieg of the Bothersome Butt-erflies": The boys use Melvin’s new animal hybrid invention to make a creature that’s a cross between a butt and a fly. But these butt-erflies are real monsters!
- "Captain Underpants and the Problematic Pandemonium of the Punishing Plungerina": After George and Harold work with Erica to create a new comic book hero, she springs off the page — and plunges into real-life crime fighting.
- "Captain Underpants and the Bombastic Blathering of Brainy Blabulous": The boys transfer to a bizarro version of Jerome Horwitz Elementary, where the teachers are nice, the kids are good… and fun is nowhere to be found.
- "Captain Underpants and the Crazy Caustic Spray of the Contagious Cruelius Sneezer": George and Harold trick Melvin into turning their bus into a time machine so they can reroute their field trip and see what ancient Rome was really like.
- "Captain Underpants and the Trashy Tale of the Tumultuous Tubbadump": The Melvins’ latest invention sends the boys’ Dump Day “trash-alanche” into another dimension — and inadvertently summons a monster.
- "Captain Underpants and the Taxing Trauma of the Treacherous Tattle Trials, Part 1": A final exam sends George and Harold to the Doom Dome, where they must battle Melvin — who’s been injected with powerful nanobots — in order to pass.
- "Captain Underpants and the Taxing Trauma of the Treacherous Tattle Trials, Part 2": Summer camp is on the line as Melvin’s nanobots find a new host in Captain Underpants, forcing the boys to shrink down and go inside his brain.
Season 3
- "Captain Underpants and the Worrisome Wedge of the Water Warmongers": George and Harold can't wait to spend the summer together at camp — but not so fast, boys, as old nemesis Mr. Krupp has an unpleasant surprise.
- "Captain Underpants and the Angry Abnormal Atrocities of the Astute Animal Aggressors": Stuck in separate camps, George and Harold unleash a hyperintelligent talking possum to scare the pants off Krupp.
- "Captain Underpants and the Abysmal Altercation of the Abominable Altitooth": Eager to get the campers out of his hair, Mr. Krupp orders them to climb Plummet Peak, where a terrifying creature is rumored to live.
- "Captain Underpants and the Bizarre Bout of the Beastly Barfilisk": George and Harold don't ask for much — just a fun scavenger hunt that does not include doing Krupp's errands; careful what you wish for, fellas.
- "Captain Underpants and the Monstrous Mayhem of the Massive Melviathan": A run-of-the-mill arts and crafts session turns into an interdimensional adventure from which George, Harold and others may never return.
- "Captain Underpants and the Savage Spite of the Slimy Salamangler": Mr. Krupp's campers take on rich rivals in a hoity-toity boat race that also features a revenge-obsessed giant salamander — paging Captain Underpants.
- "Captain Underpants and the Cunning Combat of the Covert Camoflush": The campers' splat-tastic game of paintball is rather rudely interrupted by a foul, formidable fiend known only as Camoflush.
- "Captain Underpants and the Bad Beat of the Blah Borelock": With fun in short supply, George and Harold persuade Mr. Krupp to dump the campers in the middle of the forest so they can learn to rough it.
- "Captain Underpants and the Ghastly Danger of the Ghost Dentist": The pressure is on George and Harold to tell the scariest campfire story ever; perhaps their tale of an ill-fated frontier dentist will do the trick.
- "Captain Underpants and the Confounding Concoction of the Crooked Combotato": A fierce game of plot potato takes an unexpected twist when Melvin unleashes one of his most fiendish — and carb-loaded — creations to date.
- "Captain Underpants and the Ludicrous Lunacy of the Loopy Laserlightmare": Despite being terrible at the job, Mr. Krupp wants to be the camp director again next summer, which is something that George and Harold cannot abide.
- "Captain Underpants and the Shocking Showdown of the Staggering Sugamechanger": It is parents' weekend at Lake Summer Camp, and Krupp is eager to make amends with George and Harold — or so he says.
- "Captain Underpants and the Polarizing Plight of the Pitiless Poopetrators": George and Harold want Cash Networth to buy the camp and fire Mr. Krupp, but before he'll agree to pony up the dough, Cash has a small request of his own.
- "The Spooky Tale of Captain Underpants: Hack-A-Ween": When Melvin tries to cancel Halloween, clever best friends George and Harold create their own spooky holiday — and it's a huge success.
Season 4 (aka "The Epic Tales of Captain Underpants in Space")
- "Captain Underpants and the Senseless Torment of the Space Toilet": Inspired by their favorite TV show, George and Harold — along with Principal Krupp — blast off to outer space, where an angry toilet awaits.
- "Captain Underpants and the Abandoned Artifact of the Absentee Aliens": After George and Harold learn the truth about their mission, Dupe Licitous enlists the entire crew in a quest to repair a rogue satellite.
- "Captain Underpants and the Hazardous Hysteria of the Hangry Hypnosinger": Everybody on the spaceship has been cryogenically frozen for three months — everyone, that is, except Krupp, who’s wide awake and happily in charge.
- "Captain Underpants and the Disturbing Dilemma of the Dysfunctional Doppelgängers": The crew meets their blue-hued doppelgängers when they crash-land on an alien planet where kids call all the shots.
- "Captain Underpants and the Confusing Crisis of the Conniving Captive": Melvin’s not exactly their friend… but it’s not like George and Harold can just let him be held captive by diabolical Biglyans, right? Right?!?
- "Captain Underpants and the Aggravated Assault of the Alien Armada": Oh, the indignity: George and Harold are forced to perform spa treatments on gigantic Biglyans. Also, Dr. Fitzgibbons reveals a shocking secret.