Freddie Highmore as Astro / Toby (voice)

Kristen Bell as Cora (voice)

Nathan Lane as Hamegg (voice)

Eugene Levy as Orrin (voice)

Matt Lucas as Sparx (voice)

Bill Nighy as Dr. Elefun / Robotsky (voice)

Donald Sutherland as President Stone (voice)

Charlize Theron as "Our Friends" Narrator (voice)

Nicolas Cage as Dr. Tenma (voice)

Madeline Carroll as Widget (voice)

Sterling Beaumon as Sludge (voice)

Samuel L. Jackson as Zog (voice)

David Alan Grier as Mr. Squirt / Math Cowboy / Boxer Robot (voice)

Alan Tudyk as Mr. Squeegee / Scrapheap Head / Stinger Two (voice)

Newell Alexander as General Heckler (voice)

Elle Fanning as Grace (voice)

Pilar Flynn as Cora's Mom (voice)

Dee Bradley Baker as Trashcan (voice)

Moisés Arias as Zane (voice)

Ryan Stiles as Mr. Moustachio / Burning Robot (voice)

David Bowers as Mike the Fridge (voice)

Sofia Bowers as The Little Stinker (voice)

Nicole Fletcher as "Oh No!" Kid (voice)

Maryann Garger as Dr. Pigknuckle / Newscaster (voice)

Tiffany Hillkurtz as Bride to Be (voice)

David Feiss as Cowboy Robot (voice)

Nicholas Guest as French Waiter Robot (voice)

Max Burkholder as Billy (voice)

Victor Bonavida as Sam (voice)

Steve Alterman as Press Secretary (voice)

Rif Hutton as Metro City Sergeant (voice)

Madeleine Russell as Metro City Girl (voice)

Tony Matthews as Cora's Dad (voice)