King Boo

King Boo is the powerful leader of the Boos and has a tendency to kidnap either Mario or Luigi forcing the bro that wasn't kidnapped to save the kidnapped bro. In SMG4's video's, King Boo appears in SMG4: Stupid Luigi's Mansion where he has imprisoned Mario and taken over a mansion forcing Luigi to go save his brother. Instead of freeing Mario from the painting, Luigi traps King Boo inside the painting with Mario thus allowing Mario to do some weird stuff to King Boo freaking him out.