| Person | Type | Job | Role(s) | Episodes |
|---|---|---|---|---|
 Clancy Brown | Cast | Actor | Mr. Ree / Splotch (voice) | 1 |
 David Koechner | Cast | Actor | Mr. Meaner / Mr. Neamer / Brainy Blabulous (voice) | 1 |
 Erica Luttrell | Cast | Actress | Werica Ang (voice) | 1 |
 Jorge Diaz | Cast | Actor | Snelvin Meedly (voice) | 1 |
 Kevin Michael Richardson | Cast | Actor | Diddly Saurus / The Schmoozer (voice) | 1 |
 Laraine Newman | Cast | Actress | Dr. Mentor / Ms. Ribble (voice) | 1 |
 Maggie Wheeler | Cast | Actress | Ms. Yewh / TP Mummy (voice) | 1 |
 Maurice LaMarche | Cast | Actor | Tubbadump (voice) | 1 |
 Nat Faxon | Cast | Actor | Pharaoh (voice) | 1 |
 Peter Hastings | Cast | Actor | Dr. Bagufwind (voice) | 1 |
 Sean Astin | Cast | Actor | Teachertrons (voice) | 1 |
 Steve-O | Cast | Actor | Lane Junkston (voice) | 1 |
 Tress MacNeille | Cast | Actress | Ms. Hurd (voice) | 1 |
 Eric Bauza | Cast | Actor | Robius (voice) | 1 |
 Kari Wahlgren | Cast | Actress | Mayor Hoppy McChapper (voice) | 1 |
 Dayci Brookshire | Cast | Scoops Blazer (voice) | 2 | |
 Evan Kishiyama | Cast | Choog (voice) | 1 | |
 Ramone Hamilton | Cast | Actor | George (voice) | 39 |
 Jay Gragnani | Cast | Actor | Harold (voice) | 39 |
 Patty Mattson | Cast | Miss Anthrope / Clogneta (voice) | 1 | |
| Person | Type | Job | Role(s) | Episodes |
