The Big Guy and Rusty the Boy Robot(1999)

"Big Guy" is an elite fighting robot, protecting New Tronic City from danger, whether from earth or from outer space. When the Big Guy is decommissioned, however, a smaller, childlike robot named Rusty is brought on to take its place. But it is clear that Rusty needs Big Guy's help, and it is up to the two of them to help keep the world a safer place.