Thwomps are animate cinder-blocks found mostly in the Mushroom Kingdom. They are spike-encrusted living stones, usually shaped rectangular, that made their first appearance in the game Super Mario Bros. 3. They typically attempt to flatten or squash whoever passes below them using their own weight. Sometimes, they will be moving side-to-side. As far as known, they can only be defeated by being touched by Mario when he is powered-up with a star, a raccoon or tail swipe, and hammers from hammer Mario.
Thwomps have been encountered by the crew of Gongshow:Gaiden, and severely gashed Chris's back open. He got better.