Nat Faxon
Captain Underpants / Mr. Krupp (voice)
Jay Gragnani
Harold (voice)
Ramone Hamilton
George (voice)
Sean Astin
Narrator (voice)
Peter Hastings
Comic Narrator (voice)
Jorge Diaz
Melvin (voice)
Dayci Brookshire
Jessica / Dressy (voice)
Evan Kishiyama
Steve 'Gooch' Yamaguchi (voice)
Erica Luttrell
Grace Wain (voice)
Laraine Newman
Dr. Mentor / Ms. Ribble (voice)
David Koechner
Mr. Meaner (voice)
Patty Mattson
Miss Anthrope / Clogneta (voice)
Clancy Brown
Mr. Ree / Splotch (voice)
Eric Bauza
Rap Talkwell (voice)
Kevin Michael Richardson
Diddlysaurus / The Schmoozer (voice)
Mindy Sterling
Harold's Mom / Melvin's Mom (voice)
Nolan North
Cash Networth / Salamangler (voice)
Tress MacNeille
Ms. Hurd (voice)
Maggie Wheeler
Ms. Yewh / TP Mummy (voice)
Trevor Devall
Smartsy Fartsy (voice)
Fred Tatasciore
Keithicus / Rippedicus / Guardicus (voice)
Max Koch
Hank (voice)
Steve-O
Lane Junkston (voice)
Maurice LaMarche
Tubbadump (voice)
Kari Wahlgren
Mayor Hoppy McChapper (voice)
Stephen Root
Mr. Fyde / Avacadwoe / Hush Muffleman (voice)
Brennan Murray
Bo Hweemuth / Claylossus (voice)
Jim Rash
Señor "Jerry" Citizen (voice)
John DiMaggio
Smelly Socktopus / Suds Latherman (voice)
Rob Riggle
Theodore 'Ted' Murdsly (voice)
Tudi Roche
Bernice Krupp (voice)
Paul Rugg
Vert Ladderfeller III / Altitooth / Bivouac Ladderfeller (voice)
Lewis Black
Ragely J. Snarlingtooth (voice)
Thomas F. Wilson
Major Messy / Camoflush (voice)
Dawn Wells
Gumbalina Toothington (voice)
Toby Huss
Caesar / Cruelius Sneezer (voice)
