Dry Bones (also known as Skeleton Koopas) are an undead variant of Koopa from the Super Mario universe. First appearing in Super Mario Bros. 3, these skeletal creatures have made numerous appearances since. They behave in a similar fashion to living Koopa Troopas, but Mario cannot defeat them in the same way. When a Dry Bones is stomped on, it will break apart into a heap of bones and then pull itself back together a few seconds later. They are also immune to fireballs.
The means of defeating Dry Bones varies between games, but they have been shown to be permanently defeated by the Super Cape, Super Star, POW Block, Hammer Suit, or by being blown up with Bullet Bills or Bob-ombs.