Boos first appear chronologically as antagonists to Yoshi in Super Mario World 2: Yoshi's Island. They are first seen in World 2, which featur numerous ghastly creatures. They are underlings for Kamek, the head of the Magikoopas, who turns one Boo into Bigger Boo, which grows in size every time he is hit by an egg. It serves as a minor boss. The main boss of World 2 is also a Boo-like creature, Roger the Potted Ghost, who is a normal flower pot, until Kamek makes him giant, and transforms it into a living creature. The game also features the Boo Blah, a spectacle Boo exclusive to this game. The only way to defeat Boos is by looking away and then make a egg bounce off a wall after it is thrown, hitting the ghost in the face.