|Interaction Type||Bounce Top|
If he is bounced on, Mario will start twirling and the Fly Guy will die and drop two yellow coins. Any other form of attack will not put Mario in a twirling state. There are two types of Fly Guys: ones that shoot fire and ones that don't.
Fly Guy appears in:
Mario can manipulate Fly Guy's size by running below him, causing his size to decrease. Over time, Fly Guy's size will become negative, where his visuals will become upside down. The size does not have a cap, thus it can become arbitrarily large (if negative) barring float limitations. There is no known way to arbitrarily increase his size.
This does not affect his hitbox, but it does affect the height Mario is put on when he bounces on the Fly Guy. Mario cannot bounce on Fly Guy while he has a negative size.
Size manipulation is a consequence of Fly Guy's shooting fire animation, so it can only be done on the Fly Guys that can shoot fire.