Boo is enemy in Super Mario 63 witch is a ghost. When he closes his eyes he is Invicible when he open it he can deal you damage. 

Ad blocker interference detected!

Wikia is a free-to-use site that makes money from advertising. We have a modified experience for viewers using ad blockers

Wikia is not accessible if you’ve made further modifications. Remove the custom ad blocker rule(s) and the page will load as expected.