| Paula Abdul | | Watch (voice) |
| Halle Berry | | Cappy (voice) |
| Lucille Bliss | | Pigeon Lady (voice) |
| Terry Bradshaw | | Broken Arm Bot (voice) |
| Jim Broadbent | | Madame Gasket (voice) |
| Mel Brooks | | Bigweld (voice) |
| Amanda Bynes | | Piper (voice) |
| Drew Carey | | Crank (voice) |
| Jennifer Coolidge | | Aunt Fanny (voice) |
| Dylan Denton | | Youngest Rodney (voice) |
| Will Denton | | Young Rodney (voice) |
| Marshall Efron | | Lamppost / Toilet Bot / Bass Drum / Microphone (voice) |
| Damien Fahey | | Stage Announcer (voice) |
| Lowell Ganz | | Mr. Gasket (voice) |
| Paul Giamatti | | Tim the Gate Guard (voice) |
| Dan Hedaya | | Mr. Gunk (voice) |
| Jackie Hoffman | | Water Cooler (voice) |
| James Earl Jones | | Voice Box at Hardware Store (voice) |
| Greg Kinnear | | Ratchet (voice) |
| Jay Leno | | Fire Hydrant (voice) |
| Natasha Lyonne | | Loretta Geargrinder (voice) |
| Brian Scott McFadden | | Trashcan Bot (voice) |
| Ewan McGregor | | Rodney Copperbottom (voice) |
| Tim Nordquist | | Tin Man (voice) |
| Jansen Panettiere | | Younger Rodney (voice) |
| Al Roker | | Mailbox (voice) |
| Alan Rosenberg | | Jack Hammer (voice) |
| Stephen Tobolowsky | | Bigmouth Executive / Forge (voice) |
| Stanley Tucci | | Herb Copperbottom (voice) |
| Chris Wedge | | Wonderbot / Phone Booth (voice) |
| Dianne Wiest | | Mrs. Copperbottom (voice) |
| Harland Williams | | Lug (voice) |
| Robin Williams | | Fender (voice) |
| Crawford Wilson | | Young Rodney (voice) |
| Darin De Paul | | Additional Voices (voice) |