Sumo Bro

"They're so cuuuuute! Heehee! Do you think they're related? I mean, they must be called Sumo BROS. for a reason... They're the littlest little bros. I've ever seen! We can go a little easy on them, right?"

- Olivia

The Sumo Bro (or Sumo Brother) is a type of Koopa with a similar anatomy to Boom Boom that appear as enemies to Mario. Their first appearance is in Super Mario World as somewhat uncommon enemies that can rain down fire on Mario's head by stomping.

Super Mario World
In Super Mario World, Sumo Brothers are large and orange in color and wear black shells. They also have a spike on top of their heads, meaning Mario or Luigi will be injured if they jump on one. They stand on top of blocks and attack Mario by stomping their foot (the sumo movement known as ), which causes a spark to drop below; this spark ignites when it hits the ground, making a wall of fire. A Sumo Brother can only be defeated by throwing a Shell at them, by hitting them with a cape as Caped Mario or by touching them with Mario when he is powered-up by a Super Star. Hitting the block they are standing on from below also works but is more difficult than other means due to the fires caused by their lightning-stomp attack.

New Super Mario Bros. U / New Super Luigi U / New Super Mario Bros. U Deluxe
After many years of absence, Sumo Bros. return in New Super Mario Bros. U, with the same abilities that they had in Super Mario World, except that they make electric waves instead of fire waves. Their only appearance is in the level, Screwtop Tower, and players can defeat them by hitting the platforms that they are standing on from below. They can also be defeated with ice balls, but cannot be picked up.

One Sumo Bro with a towel on his shoulders, known as Boss Sumo Bro, appears as a boss in Screwtop Tower, replacing Boom Boom. Magikoopa's magic has made him larger, and he now has the ability to jump. Unlike Boom Boom and Magikoopa, the Sumo Bro does not appear on top of the tower he guards.

In New Super Luigi U, Sumo Bros. reappear in Sumo Bro Bridge and Sumo Bro's Spinning Tower, where the boss reappears as well.

Super Mario World television series
A single Sumo Bro, known as a Fire Sumo, appears in the Super Mario World television series episode "Mama Luigi". This Fire Sumo appears to attack Luigi as he is exploring the abandoned Dome City, stomping the ground beneath Luigi hard enough to cause it to crack, sending the plumber plummeting downward.

Nintendo Adventure Books
In Unjust Desserts, some Sumo Brothers shrunken by Magikoopa are eaten by Yoshi, and two confront Mario in a tunnel inside the dinosaur. Mario defeats the two by jumping out of the way when they charge at him, causing them to crash into each other and become knocked out. If Mario smashes a Blue Shell thrown at him by a Koopa Troopa, the Sumo Brothers will awaken, but before they can renew their assault, they are sent tumbling down a passageway when the newly Winged Yoshi does a loop-the-loop. Later, some more Sumo Brothers try to attack Mario when he and Bowser's minions are forcibly ejected from Yoshi's body, but because they are still tiny, they are scared off by the seemingly giant Yoshi stomping around.

In Brain Drain, a Sumo Brother will swap minds with Wooster if he hears the static emanated by Iggy Koopa's Synapse Switcher play on a hot dog stand's radio. After unsuccessfully trying to attack both Mario and Luigi, the Sumo Brother storms off in a huff over its weak new body. Later in the book, Luigi can encounter some more Sumo Brothers if he decides to head out on his own to look for Iggy and if he manages to steal several cans of Fungus Up cola from the Synapse Switcher in the WMUSH radio station.

Mario Golf series
In Mario Golf for the Nintendo 64, "Sumo Bros." is one of the names that can appear on the tournament scorecard, while in Mario Golf: World Tour, "Sumo Bro" appears as one.

Super Mario Party
Sumo Bros. appear in Super Mario Party as non-playable characters. They appear in the minigames, Rattle and Hmmm, Absent Minded and Lightning Round. A Sumo Bro using its Super Mario World appearance also appears in Puzzle Hustle.

Dr. Mario World
Sumo Bros. appear in Dr. Mario World as assistants. Their Stage Mode skill grants a chance of earning five extra coins upon clearing a stage regardless of whether the stage is cleared or uncleared before, while their Versus Mode skill grants a 20% chance that a rainbow capsule will appear in the first 20 seconds of a match. These percentages can be increased by obtaining duplicate Sumo Bros. in Staffing.

Paper Mario: The Origami King
Sumo Bros., alongside a Boss Sumo Bro, appear in Paper Mario: The Origami King, where origami variants of them act as enemies. Olivia implies that the "bro" in their name is literal and likely related to their leader. During the battle with Boss Sumo Bro, two Sumo Bros. will accompany him on clouds, while four Sumo Bros. will land on the ground and each steal a panel: the ON panel, the Fire and Earth Vellumental Magic Circles, and the Double Attack panel. Mario must defeat the Sumo Bros. to recover the panels. Using either Vellumental Magic Circle will defeat them instantly (dealing 200 damage). After all four Sumo Bros. are defeated, the two on the clouds will land alongside Boss Sumo Bro, and will each steal a Magic Circle. They are weak to Fire Flowers.

Sumo Bros. also appear as enemies in Origami Castle. Here, they will flip certain paths if they spot Mario, who must take cover behind a wall if the Sumo Bro. is looking his way.

Super Mario World

 * Super Mario World instruction booklet: When this strange little fellow stamps its foot, lightning strikes, and turns whatever it hits into a sea of flames. BEWARE! Sumo Brother will even attack you with a karate chop!

Super Mario World: Super Mario Advance 2

 * Super Mario World: Super Mario Advance 2 "Denizens of Dinosaur Land" poster: Whenever these guys stomp their feet, lightning strikes and turns whatever it hits into a sea of flames. They are also skilled at karate and attack with mighty blows when provoked.

Dr. Mario World

 * Stage mode: "Grants 40%/60%/80%/90%/100% chance to earn extra coins (5) on stage clear."
 * Stage mode (Prior to version 2.3.0): "Grants 10%/20%/30%/40%/50% chance to earn extra coins (5) on stage clear."
 * Versus mode: "Grants 20%/40%/60%/80%/100% chance a rainbow capsule will appear within 20 seconds of match start."

Trivia

 * The Super Mario World artwork of the Sumo Brothers lacks the spike on their heads, while their plastrons are disconnected from their carapaces in a similar way to Bowser and the Koopalings. This is likely due to this design being used in early sprites. In the final game and later appearances, the spike is present and the shell is a single connected piece in the game to show that it cannot be stomped on.
 * Although they do not appear in New Super Mario Bros., New Super Mario Bros. Wii, and New Super Mario Bros. 2, their name is mistakenly applied to a related species of enemy known as Sledge Bros.
 * In Nintendo Badge Arcade, when the Arcade Bunny asks the player which character jumps a lot and resembles a sumo wrestler, one of the answers available is "Sumo Bro." (The answer is actually Mallo, as the question was asked upon starting the game on the day Pushmo badges were first made available.)