I'm looking for a 90s video game (either on the Game Boy Color or the Game Boy Advance) where you played as a robot equipped with a boomerang or a boomerang-like weapon. The weapon could be upgraded so that it could be thrown farther. Another robot followed you as a companion. I don't recall if it had an AI or if it just shot whenever you shot. I believe it was a platformer. One level took place in a forest. Another level took place underground.
The robots looked like children, and the companion was larger than the main robot (maybe it was the bigger brother of the smaller robot?). The boomerang weapon they had would glow electric blue if you got a power-up. It might have been able to pass through multiple enemies when it was glowing. The enemies may have been mostly (mutated?) animals. Some of them could fly.