Square Machine

Robot Box is an odd boss, which appears at the end of Cossack Stage 2 in Mega Man 4. It slides like the sliding slot game in Super Mario 3 for NES (and it does this at various speeds)... at its slowest speed is when it will merge together, and you need to get inside it to attack it. When it's fully formed, its weak spot--the large flashing light--will appear. Dust Crusher is the best weapon to hit it with. Ride the platforms and dodge the shots as you attack.