Bully

Bullies are Bob-omb-like creatures that lived in Lethal Lava Land during the events of Super Mario 64 and Super Mario 64 DS. A Bully resembles a black sphere with green feet, angry eyes and two bright yellow devilish horns. Bullies usually reside on Platforms and rarely in groups, to serve as a potential threat to Mario. To attack, Bullies heave themselves into their enemies in order to push them over ledges, knocking their enemies into lava or bottomless pits. The only way to beat a Bully is to push it into the lava. After being melted, a Coin will be tossed up to the platform thay the creature was pushed off from. In the remake, Yoshi, if used, must stomp them to push them back or use a cap as his tongue cannot push the Bullies. They are supposedly minions of the colossal Big Bully. Bullies attack in a similar manner as the Micro Goomba in the same game. They also appear in Bowser in the Fire Sea, the second Bowser boss level. In later games, they seem to have been replaced by Topmen.

Super Mario 3D World
Two Bullies appear in a screenshot on the Japanese website for Super Mario 3D World, hinting at their inclusion in the game.

Trivia

 * Bullies were originally going to be in Super Mario Galaxy, but were taken out.
 * Their name is a combination of bully, referring to their aggressive behavior, and bull, referring to their horns and charging attack pattern.