Thwomps first appeared in the Nintendo Entertainment System video game Super Mario Bros. 3. In the game they would await for Mario to approach them, and would then suddenly drop at an incredible velocity towards Mario in an attempt to squash him. If they succeeded, Mario would lose a life. After landing, they will slowly retreat back to the space where they were before. While they are retreating, they cannot squash again until fully recovered. Thwomps retained this basic ability in future Mario games that they appeared in.
Super Smash Bros. series
Thwomps were represented in Super Smash Bros. Melee as a collectible trophy. The following is the Thwomp's trophy description:
"Thwomps spend most of their time suspended in midair, waiting. When Mario passes below, they crash down with amazing speed. As you may guess from their appearance, they're heavy and solid enough to make any attack on them futile. Small ones are called Thwimps: despite their weight, they often form groups and bounce around."