Once you reach the part of the game where you are about to get to Sandy's house, you will find a robot. Do a spin attack near him and he will start to wobble. Get away before he comes down. Once he is down, quickly go around him to find a target sign on it. Use a hammer or spin attack for more damage, or you can use a shooting attack from far away. If it does not hit the target, he will spin out of control.