(a.k.a The Big Boo, Big Blue Boo.)
Having said that, Big Boos are very much like Bigger Boos, and their smaller cousins, Boo Buddies. They haunt ghost houses and castles, and stalk the brothers when they are not looking. If Mario or Luigi turns around, the Boos will usually hide their faces and pretend that they aren't doing anything.
Despite their timidness, Big Boos can be quite dangerous. They can be tough to get around because of their size, and they can sometimes corner unsuspecting victims who look away for too long.
Big Boos do ocassionally work for Bowser, because they are always up for some trouble, but they are more closely associated with a large gang of other ghosts, the Boo clan.
EVOLUTION:
Big Boos first appeared in Super Mario World - the Big Blue Boo was
very much like The Big Boo (see the Bigger Boo
section), except a boss. He just hung out all over the ghost houses,
getting in the way.In Super Mario World 2, The Big Boo shrunk a bit. He was still bigger than a Boo Buddy, but nothing compared to the bosses. In Super Mario RPG they shrunk again, and some people argue that the characters were mis-named, and should have been called Boo Buddies. Instead, the Lil' Boo from that game has been lumped together with Boo Buddies.
In Yoshi's Story, they grew up again, and are now somewhere between the sizes they were in SMW and SMW2.
Finally, we have a preview of what Big Boo will probably look like in the upcoming sequel to Super Mario RPG, Paper Mario. They have a very cartoony look, and seem to resemble the artwork very closely. I like them, myself, especially the transparent effect. This screenshot may actually be of a Boo Buddy, though - it's hard to tell.
"This ghost is beyond sad-he has a bad case of the Haunted House Blues. He isn't much fun, so Spin Jump over him or use a sliding Cape Attack." -Mario Mania
"Just like a monster in the movies, Big Boos like to sneak up from behind when Yoshi's not looking." -Super Mario World 2 Player's Guide
