Bullet Bills, known as Killers in Japan, are black, missile-like enemies, commonly depicted as having small arms and fanged frowns on their faces. Bullet Bills are fired by cannons known as Bill Blasters, although they are sometimes fired from other sources, such as Snifits and generic cannons. In Super Mario World they can sometimes just fly in from the edge of the screen, including the top and the bottom. Bullet Bills commonly appear as enemies or obstacles, attacking by either flying forward after being shot or actively seeking a target, either smashing into them then continuing movement or exploding on contact. In Mario Kart DS and Mario Kart Wii, the Bullet Bill is one of the usable weapons, turning any character into Bullet Bill for a brief while, speeding them ahead. Bullet Bills also make cameo appearances in Super Smash Bros. Melee and Super Smash Bros. Brawl as enemies.