Bouncing Bullet Bill

Bouncing Bullet Bills, also known as the Killer Three Bs, are a type of Bullet Bill that appear in Super Mario World 2: Yoshi's Island, Yoshi's Island: Super Mario Advance 3, and Yoshi's New Island. They can bounce off any surface that they collide with and continue flying at an angle equal to the one at which they hit the surface.

Super Mario World 2: Yoshi's Island / Yoshi's Island: Super Mario Advance 3
In their original appearances, these Bullet Bills are yellow and resemble small Banzai Bills just like their green variation. They are fired from unique swiveling yellow Turtle Cannons, and have the ability to bounce off of any surface that they come in contact with. They only appear in Raphael The Raven's Castle and Fight Toadies w/ Toadies. They cause Yoshi to drop Baby Mario if they hit him, but can be defeated with a stomp or an egg. They can also be eaten by Yoshi and spat back out to damage other enemies, or swallowed to produce an egg. After being spat out, they behave like a regular Bullet Bill in that they do not bounce off walls anymore.

Yoshi's New Island
In Yoshi's New Island, their color is changed from yellow to green, which is the color of normal Bullet Bills in the former two games. Their shape is also now that of the Bullet Bills in the current Super Mario games. They only appear in the cavern section of the level Pyro Guy Peak, where their blasters are fixed on both the ground and the ceiling. Bouncing Bullet Bills behave and can be interacted with mostly the same as in their previous appearances. However, when Yoshi spits one back out a certain distance from a wall, it will continue to rebound off incoming surfaces instead of passing right through them. Nevertheless, if Yoshi stands too close to a wall and spits a Bouncing Bullet Bill at it, it will still pass through that surface but continue to bounce off the next one.

Half of the Bouncing Bullet Bill Blasters is not modeled, like many objects in the game.

Super Mario World 2: Yoshi's Island

 * Shogakukan guide: ヨッシーはこんなものまで食べてしまう. 緑の砲台は固定式、黄色の砲台は回転式. 黄色いキ ラーは壁に当たるとはねかえる. (Yoshi would even eat this. Green cannons are a fixed type, while yellow cannons are rotatable. Yellow Bullet Bills bounce off walls.)
 * Player's Guide: Also known as Killer Three Bs. These yellow guns home in on the nearest dinosaur and fire away.

Yoshi's Island: Super Mario Advance 3

 * Shogakukan guide: とのはで、のは. いキラーは ヨッシーをいかけ、いキ ラーはかべにたるとはねる. をすならアイスで. (Green and red cannons are a fixed type, while yellow cannons are a rotatable type. Red Bullet Bills pursue Yoshi, and yellow Bullet Bills bounce off walls. The cannons can be defeated by an ice attack.)

Yoshi's New Island

 * Shogakukan guide: 砲台から放たれる巨大な弾. その名のとおり、壁や土管などにぶつかるとはね返り、飛んでいくコースが変わる. 飛ぶコースを見定めてかわすか、食べてしまおう. (A huge bullet released from a cannon. As the name suggests, when they hit a wall or a Warp Pipe, they bounce off and change course. Dodge them or eat them as they fly.)