Fly Guys are Shy Guys that have a little helicopter propeller on their heads, that allow them to fly. Their first game was in Super Mario World 2: Yoshi's Island. Ever since that game, they have appeared in multiple games, even as a playable character. His first playable game appearance is Mario Power Tennis for the GameCube. A Fly Guy also appears as a playable character in the Nintendo DS video game Mario Hoops 3-on-3, where you can unlock him by completing the Star Tournament in Hard mode.
Yoshi's Island series
Super Mario 64
Mario Power Tennis
Fly Guy is an unlockable character in Mario Power Tennis. He is classified as a tricky character and is unlocked by completing the Mushroom Cup, Flower Cup and Star Cup in singles. His Offensive Power Shot is Tornado Twist and his Defensive Power Shot is Tornado Return.
"This enemy from the Yoshi's Island series is basically a Shy Guy with a propeller on its head. It hauls items with it as it flies, so chase it down to claim a reward. Usually, it's just food but, sometimes one will have some better prizes. One could say that these ones are ... pretty fly for a Shy Guy. No? Never mind."