DR. TENMA (voiced by Nicolas Cage) – A dedicated scientific genius who's devastated and guilt-ridden when his son is killed in his lab. He works through his grief by making his robot in the exact image of his dead boy.
DR. ELEFUN (voiced by Bill Nighy) – A kindly scientist who's a colleague of Tenma, Elefun is the creator of "blue core" technology, the source of Astro Boy's awesome powers.
CORA (voiced by Kristen Bell) – A 17-year-old "surface dweller" (in 'Astro Boy,' the Earth is no longer fully habitable, and most people live in the self-contained floating metropolis Metro City). Cora is the caretaker by default of the group Astro meets when he leaves Metro City on his journey of self-discovery.
ZOG (voiced by Samuel L. Jackson) – An old-school 'bot that Astro meets on the surface and is able to power up. Zog becomes a valuable ally in Astro's battle to save Metro City.
HAMEGG (voiced by Nathan Lane) – Hamegg is a Dickensian character who leads the gang of surface-dwelling children Astro falls in with. He's instrumental in bringing Zog back to fighting form.
PRESIDENT STONE (voiced by Donald Sutherland) – President Stone, Metro City's evil commander-in-chief, is consumed by the pursuit of military power. He puts Metro City in peril when he activates the Peacekeeper robot, a superior technological weapon.
THE PEACEKEEPER – Powered by "red core" technology, the Peacekeeper is President Stone's ultimate weapon in his quest to rule Metro City with an iron fist. Unfortunately for the President -- and the people of Metro City -- the Peacekeeper malfunctions and goes out of control. Hey, it's no spoiler to say that this sounds like a job for Astro Boy.