Thwomps (also called Thwomp Traps) are semi-common enemies in the Super Mario franchise. They first appeared in Super Mario Bros. 3 These large stone creatures hide in ceilings, biding their time until Mario passes under them, and they will fall down in an attempt to crush him. They are usually either blue or gray in color, and may be covered in spikes. Thwomps are apparently immune to lava (despite being made of stone, which is not molten), as they will fall in on the castle levels, and then rise right back out. This makes them efficient elevators if you can get on top of them. Thwomps can vary in their sizes.