Zombie Wario

Zombie Wario, also known as Ghoul Wario , is one of Wario's reactions in Wario Land II, Wario Land 3, and Wario Land 4. This undead alter-ego is triggered by being touched by a zombie (Wario Land II and Wario Land 3), touched by a ghost (Wario Land II), spat at by a Skeleton Bird (Wario Land 4), or coming in to contact with Cractus's drool (Wario Land 4). When a zombie, Wario is impervious to all enemy damage, can defeat almost all enemies on touch, and fall through thin floors. On the other hand, he moves slower than before, and his jump height is reduced or in Wario Land II, could not jump at all. To return to his normal form, Wario must walk into light or fall into a body of water.

Zombie Wario appears once in Super Mario-Kun. Wario transforms into Zombie Wario by Cractus's drool. Sunlight reverts him back to normal.

Wario Land 4

 * Nintendo 3DS Ambassador Program digital manual bio: "Press to move and  to jump. You will be able to defeat some enemies you previously could not. You will also be able to slip through certain floors."

Trivia

 * The artwork of Wario Land II and Wario Land 4 show Zombie Wario lacking shoes, though his in-game sprite shows him wearing shoes. This is referenced on the Japanese website of the former, where Wario claims that the reason he walks slow as a zombie is because he wants to watch his step without shoes.