 Nat FaxonCaptain Underpants / Mr. Krupp (voice) | Captain Underpants / Mr. Krupp (voice) |
 Jay GragnaniHarold (voice) | Harold (voice) |
 Ramone HamiltonGeorge (voice) | George (voice) |
 Sean AstinNarrator / Mr Gigglenose (voice) | Narrator / Mr Gigglenose (voice) |
 Dayci BrookshireJessica / Dressy (voice) | Jessica / Dressy (voice) |
 Clancy BrownMr. Ree (voice) | Mr. Ree (voice) |
 Jorge DiazMelvin / Stanley Peet / Melvin's Dad (voice) | Melvin / Stanley Peet / Melvin's Dad (voice) |
 Peter HastingsComic Narrator (voice) | Comic Narrator (voice) |
 Evan KishiyamaSteve 'Gooch' Yamaguchi (voice) | Steve 'Gooch' Yamaguchi (voice) |
 David KoechnerMr. Meaner (voice) | Mr. Meaner (voice) |
 Erica LuttrellErica / George's Mom (voice) | Erica / George's Mom (voice) |
 Patty MattsonMiss Anthrope / Harold's Mom (voice) | Miss Anthrope / Harold's Mom (voice) |
 Brennan MurrayBo Hweemuth (voice) | Bo Hweemuth (voice) |
 Kevin Michael RichardsonDiddlysaurus / George's Dad (voice) | Diddlysaurus / George's Dad (voice) |
 Mindy SterlingMelvin's Mom (voice) | Melvin's Mom (voice) |
 Stephen TobolowskyCreepy Rattlechains (voice) | Creepy Rattlechains (voice) |
 Kari WahlgrenMayor Hoppy McChapper (voice) | Mayor Hoppy McChapper (voice) |
