Boos are spherical-shaped ghost creatures from the Super Mario franchise. These mischievous spirits are frequently found in darker areas of the Mushroom Kingdom such as old abandoned houses and creepy forests. Their mouths are always hanging open and revealing their fangs and long tongues. Oddly enough, Boos are quite shy and they stop in place and cover their faces when they're being looked at, but will continue to give chase when their prey looks away.