Fryguy

Fryguy is the boss of World 4 in Super Mario Bros. 2. He is a living ball of fire created by Wart during the frog tyrant's conquest of Subcon.

Super Mario Bros. 2
During the events of Super Mario Bros. 2, Fryguy was stationed in a tall fortress at the end of World 4. Ironically, despite being a living embodiment of flame, World 4 was a land of snow, ice, and arctic oceans. When confronted by Mario and his friends, Fryguy became enraged and spewed fireballs to attack the heroes. Since Fryguy was made of fire, Mario would be damaged if he happened to touch the living embodiment of flame. To defeat Fryguy, Mario had throw Mushroom Blocks at the fire monster. After three hits, Fryguy would be defeated (in a sense). After being destroyed, Fryguy would split into four Mini Fryguys. Before the battle could truly be won, Mario had to "snuff out" these tiny hopping flames as well.

The Super Mario Bros. Super Show!
Fryguy was a character in The Super Mario Bros. Super Show!. Like many enemies on the show, the fire monster worked for King Koopa, as opposed to Wart (as in the video games). Fryguy did not appear as much as other Super Mario Bros. 2 enemies on the show.

Nintendo Comics System
Fryguy also appeared in the Nintendo Comics System's Mario comics. In the comics, there was not one Fryguy, but multiple Fryguys. Also, these Fryguys were not magically created living fireballs; these Fryguys were created when a Toad becomes engulfed in fire or lava. In one comic story, "Duh Stoopid Bomb!", a sole Snifit becomes a super-genius after being exposed to one of Bowser's inventions. This Snifit than performs a coup and takes over Bowser's Castle. After the coup, Bowser is expelled to "Fryguy Kindergarten".

Trivia

 * In the Super Mario Bros. movie, the flamethrowers used by King Koopa and his minions are referred to as "Fryguy Flamethrowers".
 * A Sammer Guy in Super Paper Mario is called Guy Who Fry.