Big Blue Boos inhabit some of the Ghost Houses located around Dinosaur Land. Curiously, although they are over ten times bigger than a normal Boo, Big Boos still have the same mannerisms of their smaller counterparts. Of course, this means that when looked at, a Big Boo will fade and hide behind its arms. However, if Mario's back is turned to a Big Blue Boo, it will attack Mario from behind by floating towards him.
In the game, Big Boos are much more difficult to pass than their smaller brethren. As such, Mario usually has to use a trampoline to jump over these massive ghosts. However, if Mario can get a running start, they can usually Spin Jump over a Big Boo. Additionally, if there is room, Mario can use a cape to fly over a Big Boo or perform a sliding Cape Attack during descent to actually destroy the Big Boo.