Dry Bones are skeletal versions of Koopa Troopas mainly found in towers and castles. These undead Koopas often collapse when attacked, but they soon revive themselves and become normal once again (however, there are some methods to permanently defeat them). Dry Bones first appeared in Super Mario Bros. 3, in which sprites of them are edited Koopa Troopa sprites. They have since become a staple in Mario spin-off games. Dry Bones is ordinarily a lightweight character in games and is often accompanied by Boo. The Dry Bones emblem in spin-offs is a side-view of one's head.
The Wario franchise is the first franchise created by Nintendo to feature a villain/antihero as the main protagonist.
Double Mario from Super Mario 3D World was actually the result of a mistake made by a staff member with the placement tool, which created two player Marios. The staff thought it was a good idea and decided to include it in the game.