Fuzz Ball

Fuzz Balls are white, ghost-like monsters with a single eye and a wagging tongue, found in Fortresses. They follow a variation of swooping tactics; all Fuzz Balls in a chamber (typically four) fly in an unalterable pattern, waving vertically as they travel horizontally. This creates a diagonal pattern that sweeps across the entire chamber. Taking out a Fuzz Ball or two doesn't change the pattern and makes that part of the chamber no longer a danger. They can travel through walls.

Kid Icarus: Of Myths and Monsters
"Flies around the Fortress like it owns it."