Mechakoopas made their first appearance in Super Mario World, where they were Bowser’s main weapon of choice during the final battle. Bowser fought entirely from the Koopa Clown Car in that game, but nowadays that’s more Bowser Jr.’s thing, who uses Mechakoopas as his down special. They’ll be deployed on the ground, marching along at a steady pace. They’ll explode on contact, or after a small amount of time.