Grim Leecher

Grim Leechers are enemies from Super Mario World 2: Yoshi's Island and Yoshi's Island: Super Mario Advance 3 that exclusively appear in the levels The Impossible? Maze and Mystery of the Castle? These enemies resemble purple ghosts with skulls on their faces. If Yoshi is a good distance from a Grim Leecher, they will wait until Yoshi comes near, but then hover towards Yoshi if he comes too close. If they come in contact with Yoshi, the Grim Leecher will kick Baby Mario off Yoshi's back and hop on. This will cause the game controls to reverse and Yoshi will be coloured pink.

Trivia

 * Their name is a pun on the "Grim Reaper" and "Leech".