From the Super Mario Wiki
Zombie Wario.
is another of
Wario's famous transformations in the
Wario Land series of games. This creepy alter-ego is triggered by being touched by a ghost, spat at by a skeleton, or touched by a zombie enemy in
Wario Land 2-4. When a zombie, Wario is imprevious to all enemy damage, can defeat almost all enemies on touch, and fall through thin floors, making it quite useful at times. Unfortunately, he moves at a very slow speed, and can barely jump (in his first appearance in
Wario Land 2, he couldn't jump at all). To return to his living form, Wario must walk into light or fall into a body of water. He also sometimes falls apart and then might come alive again.
