Fly Guys are a type of Shy Guy found in several Super Mario Games. The only difference is that they have a propeller on their head and are able to fly around.
Super Mario 64/Super Mario 64 DS
Fly Guys originally appeared in the game Super Mario 64. They are found in Dry Dry Desert and Rainbow Road. Once jumped on, they will give Mario a short aerial boost. They will fly towards Mario to attack him.