The Bullet Bill is a common enemy which appears in Super Smash Bros. Brawl's Subspace Emissary mode. They fly from right to left, exploding upon impact with a character or on the ground. They also appear in Donkey Kong's introduction, in which three of them are destroyed by Diddy Kong. They can be reflected, but will quickly right themselves and continue their attack. Some of them are guided missiles, following players until they hit.
A shell fired from a special cannon known as a Bill Blaster. Easily identified by their angry eyes, Bullet Bills fly across the land in perfectly straight lines. Though they easily shrug off fireballs, they can be stopped by jumping on them. A unique characteristic of the cannons is that they will not fire a Bullet Bill if Mario is standing right beside one.
Bullet Bill returns in two various versions; one as an item, and one as a common enemy for Smash Run.
As an item, any character who obtains it can turn into a Bullet Bill, and charge towards enemies in a multitude of directions.
In Smash Run, Bullet Bills appear as a common enemy and during the "Bullet Bill" fest. Bullet Bills can also be launched out of Bill Blasters. When not being launched out of Bill Blasters, they will hone in on the player. When launched out of a Bill Blaster, they will fly in the same direction they were launched from. Touching a Bullet Bill will cause fire damage. If a Bullet Bill crashes into a wall, they will explode, but will not drop powerups if killed this way.
Strangely, even though they can be jumped on in the Mario games, players will be damaged even if jumped on in the Subspace Emissary/Smash Run.