Bull's-Eye Bill

Missile Bills (also known as Heat-Seeking Bullet Bills), are purple Bullet Bill variants that have heat-seeking visuals.

Their first appearance was in Super Mario Bros. 3. In this game, a Missile Bill would turn around once if it missed its target, but would continue going forward without turning around anymore after missing twice.

They make another appearance in Super Mario Sunshine at Pinna Park's beach. In this appearance, they are purple and shot from the Monty Mole's cannon. They always home in, so there is no way Mario can easily outrun them. They can destroy the baskets on the beach which hold Blue Coins; this is the only way to open them. Missile Bills explode when they make contact with an object, or if Mario squirts water at them. There is a gold version that will make coins appear if Mario jumps on it. During the final battle, Bowser Jr. sends some regular ones and also a blue one that will let out a 1-Up Mushroom or a Water Bottle if stomped on.

They also reappear in New Super Mario Bros. Wii, though they were referred to as Heat-Seeking Bullet Bills in the Prima game guide. Here, they have a similar attack pattern to the one they did in Super Mario Bros. 3. However, in this game, they can change the angle they are flying at and will not stop pursuing the player until they are defeated or the player has gotten far enough away. They only appear in World 9-3, alongside a new sub-species, Missile Banzai Bills.

Trivia

 * Although Missile Bills do not appear in Super Mario 64, Super Mario Galaxy, and Super Mario Galaxy 2, Bullet Bills in those games act the same way by homing in on Mario.
 * They were going to make a surprising reappearance in Mario & Luigi: Superstar Saga but were scrapped for a reason unknown.