Thwomp

Thwomp is a animate cinder-block enemy found in many games from the Mario series.

Character description
Thwomps make their debut appearance in Super Mario Bros. 3. They usually try to squish Mario under their weight whenever he passes beneath them. Thwomps are possible to be easily avoided by using the Statue Mario ability. With this, it is impossible for Thwomps to destroy Mario by crashing him from above. They return in the game's remakes, Super Mario All-Stars and Super Mario Advance 4: Super Mario Bros. 3 in the same fashion as the older Thwomps. They feature improved graphics and retake their especially mad expressions. Curiously, these Thwomps have a "bigger spike" on top of their forehead, separated from the rest of the body by what looks like a small ribbon of sorts. This spike is prominent in appearance but has no effect in the game. It is also worth noting that these Thwomps, instead of having their eyes separated, have both eyes as glowing dots in a black space. This is most likely due to palette and space limitations.

In Super Smash Flash 2
In Super Smash Flash 2, a Thwomp appears on Bowser's Castle as a stage hazard. At certain intervals, it randomly falls at high speed towards the ground, smashing the platform and sinking said potion into the damaging lava below. If the Thwomp directly "crushes" any character on its way down, it will deal 21% of damage and deal some considerate knockback; based on the position the character was located when he/she was crushed by the Thwomp, coupled with the low upper blast line of the stage, it can potentially result in a one-hit KO. The Thwomp itself acts as another platform as well, and characters can stand on its top, this may be potentially dangerous, though, as staying on the Thwomp for too long as it is rising may also result in a KO.