Flat Wario

Flat Wario is one of Wario's many, many transformations in the Wario Land game series. If crushed by a falling weight in Wario Land 2-4, Wario will be squashed flat, shortening his jump and drasticlly affecting his speed. However, he can glide smoothly in the air to reach places previously unattainable, and slip through tiny cracks in walls. Certain machines and enemies will return Wario to his original shape, as well as getting wet.

Also, in Wario World, the boss DinoMighty can stomp Wario into the ground and flatten him, although there is absolutely NO use for this.