Thwimp is a cubic, mostly grey figurine whose scalp and temples consist of four small one-by-one pyramids (twelve in total). It has an unhappy look on its face. Its action tile is on the back and it requires three stomps to defeat.
Thwimps were a minor foe introduced in Super Mario World in 1990. They were cubic beings who would usually appear in groups of two and hop back and forth in large arcs trying to land on the Mario Brothers.