Fireball

Fireballs were the first generic enemies ever in a Mario game. In Donkey Kong, the fireballs would jump out of oil barrels and try to harm Mario by touching him. One touch and Mario was dead. They could be destroyed with a Hammer.

They appear in Mario vs. Donkey Kong 2: March of the Minis in the final boss fight with Donkey Kong on the roof.

It's possible they're related to Podoboos, Embers, Lava Bubbles, Sparkys.