From the Super Mario Wiki
Hotheads are large balls of sparking energy that first appear in the game Super Mario World.
Super Mario World
Hotheads first appear in Super Mario World. They slowly move around platforms and don't pose much of a threat. These creatures only appear in some of the fortresses and castles. They can usually be found in areas with Li'l Sparkys, which are smaller versions of Hotheads.
Super Princess Peach
Hotheads reappear in Super Princess Peach. They behave similarly to how they act in Super Mario World. Unlike most other enemies in the game, Hotheads do not have a Vibe-based counterpart.
Super Smash Bros. series
Hotheads appear as an item in Super Smash Bros. Brawl and Super Smash Bros. for Nintendo 3DS / Wii U. Like in Super Mario World, they stick to the stage when thrown and burn anyone that touches it. It will also grow larger if hit with attacks, but it grows significantly larger when hit by fire and electric attacks. Hotheads move quickly around the platform they are on, but can also just fall off entirely.
Super Smash Bros. Brawl
|| SNES Super Mario World
|| An item that, when tossed, sticks to the terrain and moves, causing damage to those it touches. Whoever threw it won't take damage. It will grow larger if it's attacked, which ups its attack range. However, an increase in size corresponds to a decrease in the time it stays on the screen. A really big Hothead will take up the entire screen, and is quite a sight to behold.
Super Smash Bros. for Nintendo 3DS / Wii U
(Wii U version only)
||SNES Super Mario World (08/1991)
NDS Super Princess Peach (02/2006)
|Once thrown, this guy will move across the ground and damage everything--except you--in its path. You can make the Hothead bigger by hitting it with attacks, much to opponents' dismay. If you make it really big and powerful, it may just carry you to victory!
Names in other languages
|From ケセランパサラン, legendary Japanese creature.
||Großschein (since Super Princess Peach)
Hothead (Super Mario World)
Sfavillo (Super Princess Peach)
|Onomatopoeia of electric sparkling