From the Super Mario Wiki
“I'm too hot to touch!”
Fryguy is the boss of World 4 in Super Mario Bros. 2. He is a living ball of fire created by Wart with the Nightmare Machine during the frog tyrant's conquest of Subcon. Fryguy first debuted in his first model, Yume Kojo: Doki Doki Panic.
 Super Mario series
 Super Mario Bros. 2
During the events of Super Mario Bros. 2, Fryguy is stationed in a tall fortress at the end of World 4, since their conquest is almost complete. Despite Fryguy's being a living flame, World 4 is a land of snow, ice, and arctic oceans of Subcon. When confronted by Mario and his friends, Fryguy becomes enraged and spits fireballs to attack the heroes. Since Fryguy is made of fire, Mario takes damage if he happens to touch the living embodiment of flame. To defeat Fryguy, Mario has throw Mushroom Blocks at the fire monster. After three hits, Fryguy splits into four Mini Fryguys. Before the battle can be won, Mario has to defeat these tiny hopping flames as well.
 BS Super Mario USA
Fryguy appears once again as a boss in the sequel, BS Super Mario USA. He helps Wart and the other 8 bits attack Subcon once more, but is eventually defeated by Mario and the other heroes once again. Like the predecessor, he is found in the snowy lands of Subcon and he is fought in a very similar way to that of Super Mario Bros. 2.
 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".
 Nintendo Adventure Books
 Other References
In the Super Mario Bros. film, the flamethrowers used by Koopa and his minions are referred to as "Fryguy Flamethrowers".
 Names in Other Languages