Bullet Bills are recurring enemies in the Mario series. They are black, bullet-like enemies, commonly depicted as either having small arms or fanged grins adorning their faces, rarely having both. Bullet Bills are fired by cannons known as Bill Blasters, although some games have them fired by other sources such as Snifits and generic cannons, while some games simply have them coming out of nowhere. Subspecies of Bullet Bills include Banzai Bills and Cat Bullet Bills.
Bullet Bills commonly appear as obstacles in games, attacking by either flying forward after being shot or actively seeking out a target, either smashing into a them and continuing on their way or exploding on contact, as most recent games portray them as doing. Spin-off games, such installments of the Mario Party series and Mario Kart DS feature Bullet Bills as items which can be used plow into and injure opponent characters. Perhaps due to the name and nature of the enemy, Bullet Bills only appear in two episodes of DIC Entertainment's Super Mario cartoons, but are featured with much more prominence in literature such as comics and books. The live-action Super Mario Bros. movie feature miniaturized Bullet Bills, though not named as such, as the power source of the "Thwomp Stomper" boots; a neon sign advertising a bar named "Bullet Bills" can also be seen throughout the film.
Since Mario Kart DS, the player can collect Bullet Bills as items from item boxes. Upon using the item, the user will transform into a near (if not completely) invincible Bullet Bill and rocket down the track on Auto-Pilot for a few seconds, knocking over any enemies and players in the way and stripping players of their items, similar to the Chain Chomp from Mario Kart: Double Dash!!. The Bullet Bill can only be received by the drivers on sixth to eight place (sixth to twelfth in the case of Mario Kart Wii). However, this item can sometimes be a curse. When on the trickier, narrower courses, these can sometimes lead racers up to a sharp turn or obstacle on the track and then end, possibly causing the kart to fall off the track and lose some of the spots gained using that item but the perks overshadow the cons of using it. Players can avoid this item if they are far ahead of the person using it, invincible, or out of the flight path. This is also one of four items which can be used to dodge a Blue Shell (the others being a Mushroom, a Starman, and Mario Kart Wii's Mega Mushroom).
Bullet Candy - Mario Party 8 - The Bullet Candy is a rare type of candy found only on the Mario Party 8 board, Bowser's Warped Orbit. When triggered, the player transforms into a Bullet Bill, allowing them to roll three dice blocks. Any opponent caught within the player's path will lose one star.
In Yoshi's Island, Bullet Bills make several appearances. The most common Bullet Bill is green, shooting in a straightforward manner. Yellow Bullet Bills can bounce off of walls, while Red Bullet Bills will track Yoshi and continuously follow him.
Bullet Bills are uncommon enemies that appear in Super Mario Sunshine. They are usually seen being fired from certain enemies such as a Monty Mole cannon, Mecha Bowser, and Bowser Jr.'s small boat. Bullet Bills follow after Mario until they collide with him or explode themselves. There are also pink Bullet Bills that does more damage to Mario but release a lot of coins. These Bullet Bills are helpful for the 100 Coin Shine Sprite mission such as Pinna Park. These bullet bills also have a mouth shaped into a smile.
Due to their firing method and relatively large size, Bullet Bills are more closely related to cannon balls than actual bullets.
Using real-life physics, Bullet Bills would not actually cause much harm to a person due to their relatively slow movement velocity.