Snufit

Snufits are ghostly versions of Shy Guys in Mario 64. They are red, Boo-like figures wearing white masks that float around in Hazy Maze Cave and Cavern of the Metal Cap. There is a mouth-like protrusion on their mask that they shoot bullets from to damage Mario. They can be defeated by being jumped on, or being touched when Mario wearing the Metal Cap.

Enemy Discoloration
In some personalized copies, the Snufits are said to have gray masks instead of white. This more closely matches their modern appearance and their design in the DS remake. It is possible that this discoloration is what influenced their redesign. There is no notable change in behavior between them and their normal white counterparts.