Grim Leecher

Grim Leechers appear in the "The Impossible? Maze" level of Super Mario World 2: Yoshi's Island. They resemble purple ghosts with skulls on their faces. If Yoshi is too far away, they will just sit waiting, but then hover near Yoshi if he comes too close. If they came into contact with Yoshi it would ride his back, kicking Baby Mario off. This would reverse the games controls and Yoshi would change colors.

Trivia

 * "Grim Leecher" is most likely based off Grim Reaper.