From Sonic Retro
It's an egg-shaped robot with long spinney arms and detachable disks on top of their heads. They remain still when idle, but when an enemy is detected they will release the disk, which will hover around casting a conical laser beam much alike the common science fiction for an UFO abducting someone. When a character is caught inside the beam they'll be stunned momentarily and the Egg Keeper will then try and ram them with its body. An Egg Keeper can only be destroyed when the disc is detached, otherwise, they'll slap the character away if they come too near.