Main •
Nat Faxon as Benjamin "Benny" Krupp/Captain Underpants • Ramone Hamilton as George Beard • Jay Gragnani as Harold Hutchins •
Sean Astin as Narrator •
Peter Hastings as Comic Narrator •
Jorge Diaz as Melvin Sneedly, Stanley Peet, Mr. Rected, and Melvinborg •
Erica Luttrell as Erica Wang
Supporting •
David Koechner as Mr. Meaner •
Laraine Newman as Ms. Ribble • Patty Mattson as Ms. Anthrope • Dayci Brookshire as Jessica Gordon, Dressy Killman, Penelope Brown-Hoggard and additional teachers. • Grace Dumbaar as Sophie One • Evan Kishiyama as Steve "Gooch" Yamaguchi • Brennan Murray as Bo Hweemuth •
Trevor Devall as Smartsy Fartsy and new Smartsy Fartsy (who was eaten by Smartsy) •
Nolan North as Lee Dingman, Cash Networth, Jet Wingman, Yule, and Dr. Shifty Fitzgibbons • Secunda Wood as Moxie Swaggerman and Haily Comett • Gavin C Robinson as Mr. Hand •
Tress MacNeille as Ms. Hurd •
Kevin Michael Richardson as Diddlysaurus, Dr. Diaper, Turbo Toilet 2000, Zorx, Klax, Jennifer, Professor Poopypants, The Schoozer, and Fingers •
Stephen Root as Morty Fyde and Avacadwoe •
Mindy Sterling as Cindy Sneedly •
Clancy Brown as Toilette Ree and Splotch •
Phil LaMarr as Mr. Cleveland •
Maggie Wheeler as Ms. Yewh, TP Mummy, and Lunch Lady •
Tudi Roche as Bernice Krupp •
Stephen Tobolowsky as Creeply Rattlechains •
Fred Tatasciore as Furculees, Chief Hairococha, Keithicus, Rippedicus, and Guardicus •
Rob Riggle as Theodore "Ted Turdsly" Murdsly •
Dawn Wells as Gumbalina Toothington •
Steve-O as Lane Junkston •
Jim Rash as Mr. Jerry Citizen •
Lewis Black as Ragely J. Snarlingtooth •
Toby Huss as Caesar and Cruelius Sneezer •
John DiMaggio as Smelly Socktopus •
Gary Anthony Williams as Dupe Licitous •
Paul Rugg as Vert Ladderfeller III, Altitooth, and Bivocac Ladderfeller •
Maurice LaMarche as Tubbadump • Max Koch as Laserlightmare and Hank •
Jim Cummings as
Santa Claus/Jacked Santa •
Eric Bauza as Robius and Rap Talkwell •
Kari Wahlgren as Mayor Hoppy McChapper ==Production==