| Freddie Highmore | ... Astro, Toby (voice) |
| Kristen Bell | ... Cora (voice) |
| Nathan Lane | ... Hamegg (voice) |
| Eugene Levy | ... Orrin (voice) |
| Matt Lucas | ... Sparx (voice) |
| Bill Nighy | ... Dr. Elefun, Robotsky (voice) |
| Donald Sutherland | ... President Stone (voice) |
| Charlize Theron | ... "Our Friends" Narrator (voice) |
|
| and |
| Nicolas Cage | ... Dr. Tenma (voice) |
|
| Ryan Stiles | ... Mr. Moustachio, etc. (voice) |
| David Alan Grier | ... Mr. Squirt, etc. (voice) |
| Alan Tudyk | ... Mr. Squeegee, etc. (voice) |
| Newell Alexander | ... Gen. Heckler (voice) |
| Bob Logan | ... Stinger One (voice) |
| Dee Bradley Baker | ... Trashcan (voice) |
| Moises Arias | ... Zane (voice) |
| Sterling Beaumon | ... Sludge (voice) |
| Madeline Carroll | ... Widget (voice) |
| David Bowers | ... Mike the Fridge (voice) |
| Elle Fanning | ... Grace (voice) |
| Sofia Bowers | ... The Little Stinker (voice) |
| Samuel L. Jackson | ... Zog (voice) |
|
| Additional Voices |
| Nicole Fletcher | ... "Oh No!" Kid (voice) |
| Maryann Garger | ... Dr. Pigknuckle, Newscaster (voice) |
| Tiffany Hillkurtz | ... Bride to Be (voice) |
| David Feiss | ... Cowboy Robot (voice) |
| Nicholas Guest | ... French Waiter Robot (voice) |
| Max Burkholder | ... Billy (voice) |
| Victor Bonavida | ... Sam (voice) |
| Steve Alterman | ... Press Secretary (voice) |
| Rif Hutton | ... Metro City Sergeant (voice) |
| Madeleine Russell | ... Metro City Girl (voice) |
| Pilar Flynn | ... Cora's Mom (voice) |
| Tony Matthews | ... Cora's Dad (voice) |
