Wart is a fictional character most commonly recognized from Super Mario Bros. 2, known as Super Mario USA in Japan, in which he is the ultimate villain. However, Super Mario USA is actually an adaptation of a game called Doki Doki Panic by a company called Fuji TV. Nintendo bought the rights to the game and replaced the main characters with characters from the Mario series, and was released in America as the sequel to Super Mario Bros (the true sequel to SMB was released in Super Mario All-Stars (SNES) as a game entitled The Lost Levels). Thus Wart was originally a Fuji TV character and he, as with the other characters in Doki Doki Panic/SMB USA, originally held no relation to the Mario universe. Nonetheless, as many of the enemies from Doki Doki Panic have appeared in later Mario games (most popular perhaps being the Shy Guy), Wart has been incorporated into the Mario universe in several intersesting ways. He is said by fanon to be related to Bowser (perhaps due to the fact that some of Wart's own minions have been shown to be working for Bowser), and he gets defeated by Mario, Luigi, Peach, and Toad. Wart hates vegetables, so Mario and his friends have to defeat him by bombarding him with them.

Strangely, Wart never appeared in the Mario cartoons, yet his many minions were regulars during the first season. However, he did appear in one comic story published for the Nintendo Comics System. Titled "Cloud Burst", this story has Princess Peach's father, King Toadstool, looking to buy a new mattress as his current one is too lumpy. Disguised as a bed salesman, Wart takes the King up into the clouds and advertises a bed-shaped raincloud as a "Cloud Nine" mattress. As the King rests up on that cloud, it causes rain all over the Mushroom Kingdom, but is quickly patched up by the Mario Bros. Although this was Wart's only comic appearance, one particular line of dialogue from Mario seemed to suggest that Wart frequently kidnapped the King in that continuity.

Wart also appeared in book six of the Nintendo Adventure Books , titled Doors to Doom. There, though, he appeared as a skateboarder who ended up helping the Mario Bros. during their current plight. This cameo of his may have inspired how, in some fan-based material, he's actually a good king who may have been corrupted by Bowser.

Wart later appeared in The Legend of Zelda: Link's Awakening, in which he was referred to as Mamu (his Japanese name). In that game, he was a musician and taught Link a song.