Bomps are a subspecies of a Thwomp. They try to push Mario off his current elevation. They mainly act in a similar manner as if they were obstacles. Bomps are indestructible in all of their appearances.
Super Mario 64 / Super Mario 64 DS
Bomps first appear in Super Mario 64. Encountered first in Whomp's Fortress, these moving roadblocks appear in the same style as the walls that surround them, except they have eyes. Their eyes appear blue in color. Found early in the level, their role is to push Mario off the cliff to the platform below, wasting time. Out of the Bomps found here, the ones at the beginning and end of their row appear thinner than the ones found in the middle of the row. They are also found in other levels, such as Lethal Lava Land. In Super Mario 64 DS, they do not have eyes.