Bill Blaster and Bullet Bill
Bill Blasters are stationary cannons which fire Bullet Bills in a straight line across the stage. They can usually shoot in both directions, and are completely indestructible in most Mario Games. Bullet Bills are simply the missiles that they shoot out. This dynamic duo first appeared in the original Super Mario Bros.
Roy Koopa carries a Bill Blaster and shoots Bullet Bills as he jumps around.
Appearance: Bill Blasters are pitch black, shiny cannons with a skull emblazoned on their sides. Bill blasters are completely invincible, so don't waste time trying to destroy them. Bullet Bills are missiles that look like a normal bullet. They have angry eyes which are always looking forward towards their target, and they also sport a pair of arms, their hands always balled into fists. In some of the Mario games, the also have a mouth with sharp teeth, much like Banzai Bill, or they have a really big grin on their face.
How to defeat them: Bill Blasters are completely indestructible in New Super Mario Bros. U. In games with the Mega Mushroom it was possible to bulldoze through them, but due to the absence of said Mushroom in this game, they are once again invincible. Bullet Bills however, can be jumped on and easily taken care of. They are completely immune to fire so hold your...umm...fire. However Bullet Bills can be frozen, picked up while in midair and tossed into other enemies. In some levels, it is possible to keep a large group of Bullet Bills in the screen with you and get them to the end of the level, jumping on the flagpole to end all of them at once. Doing so usually awards Mario with several lives and the player with a grand feeling of satisfaction.
Trivia: There are other types of Bullet Bills such as Banzai Bills and the indestructible, King Bill.
In some Mario titles, Bullet Bills are shown as beings with emotions and reason, not just angry projectiles.
Bullet Bills make a cameo appearance in Super Smash Bros. Brawl in the Subspace Emissary, acting in their usual manner.
Bullet Bills are an item in Mario Kart which carries the user to the front of the pack, following the track for the player and completely blowing through anything in their path.