The Bigger Boo is an enormous Boo that appears as a boss in Super Mario World 2: Yoshi's Island. This creature was a regular Big Boo, but when the Yoshis reached its fort, Kamek the Magikoopa used his magic to make the Big Boo super-sized. After its growth, the Bigger Boo takes up most of the boss-room, giving Yoshi limited space to move around.
During the boss fight, the Bigger Boo behaves in the same manner as standard Boos, chasing Yoshi when his back is turned and remaining still while being looked at. When still, the Bigger Boo becomes intangible so Yoshi cannot attack it. To defeat the boss, Yoshi must fire his eggs at the walls and floors while not facing Bigger Boo. If thrown at the right angles, the eggs will ricochet off the walls and hit the Bigger Boo, though this will also cause it to increase in size, further limiting Yoshi's maneouvring space. After being hit five times, the Bigger Boo will expand to the point where it explodes.