The Mechanical Piranha Plant is a cardboard-like verson of a Piranha Plant that appears in Waluigi Stadium in Mario Kart: Double Dash!! and Mario Kart Wii. They pop out from cardboard-like tubes and act like a real Piranha Plant, opening and closing their mouth. If you run into one, you will be temporarily stopped until you can steer your way around. Even being powered up by a Star is not powerful enough to destroy one of these and the kart will simply stop if done so.