Nat Faxon
Captain Underpants / Mr. Krupp
Sean Astin
Narrator / Mr Gigglenose
Dayci Brookshire
Jessica / Dressy
Jorge Diaz
Melvin / Stanley Peet / Melvin's Dad
Peter Hastings
Comic Narrator
Evan Kishiyama
Steve "Gooch" Yamaguchi
David Koechner
Mr. Meaner
Erica Luttrell
Erica / George's Mom
Patty Mattson
Miss Anthrope / Harold's Mom
Brennan Murray
Bo Hweemuth
Kevin Michael Richardson
Diddlysaurus / George's Dad
Mindy Sterling
Melvin's Mom
Stephen Tobolowsky
Creepy Rattlechains
Kari Wahlgren
Mayor Hoppy McChapper