Originally intended to be kept a secret, Astro Boy, a Pinocchio-like character, becomes a publicly renowned superhero — complete with devices such as laser-firing fingers, uncanny hearing, and jet-powered boots — all eventually used to repel an alien invasion of Earth.
Dr. O'Shay activates Astro by drawing all of the city's power and using it to jolt Astro to life. But the power surge overloads the Metro City Power System, turning Magnamite, the robotic power-controller, into a robotic menace. When Magnamite comes crashing across the city like a huge mechanical octopus, Astro must master his amazing powers quickly in order to save the city from the rampaging robot.