Ghost Guy

Shy Guy Ghosts are undead Shy Guys that appears in the game Luigi's Mansion. They are red with Shy Guy masks and are equipped with pitchforks resembling the one carried by Beezos from Super Mario Bros. 2 and the non-Mario game Yume Kojo: Doki Doki Panic. When Luigi uses the vacuum on them the masks come off revealing two yellow eyes in a dark void.

Mario vs. Donkey Kong has another same named enemy, they comes in three different colors (red, blue and yellow like the Viruses from Dr. Mario) and if Mario pushes the button with the same color it transforms into a block (or a regular Shy Guy when fighting Donkey Kong). They only appear in the level Spooky House.

Other similar enemies are Boo Guys and Phantom Guys.