Sumo Bro

Sumo Brothers are a sub-species of Hammer Brothers who first appeared in Super Mario World.

''Super Mario World
In Super Mario World, Sumo Bros. are large and orange in color and wear black shells, they also have a spike on top of their head, meaning Mario or Luigi will injure himself if he jumps on one. In Super Mario World, Sumo Brothers would stand on top of blocks and attack Mario by stomping their foot (the sumo movement known as shiko), which will cause a spark to drop below; this spark will ignite when it hits the ground, making a wall of fire. Sumo Bros. could only be defeated by throwing a Shell at them, by hitting them with a Cape as Cape Mario or by touching them with Mario when he is powered-up by a Starman. Hitting the block they are standing on from below also works, but is more difficult than other ways due to the fires caused by their lightning-stomp attack.

''New Super Mario Bros.
Sumo Bro. have yet to appear again in a game after Super Mario World. However, in New Super Mario Bros., their name was mistakenly applied to the unrelated species of enemies known as Sledge Bros. This error was remedied in New Super Mario Bros. Wii.

"Mama Luigi"
A single Sumo Bro., though called a Fire Sumo, appeared in the Super Mario World episode "Mama Luigi". This Fire Sumo appears to attack Luigi as he is exploring the abandoned Dome City; this Fire Sumo ends up stomping the ground beneath Luigi hard enough to cause it to crack, sending Luigi plummeting downward.

Trivia

 * The Sumo Bros.'s artwork lacks the spike on his head. However, the spike is present on the game sprite and on the TV show.