| King Boo|
— Boo, Super Mario 64
“Ghost don't DIE... Heh, heh, heh. Can you get out of here... ALIVE?!”
Ghosts are a species that appear (at least) once in many video games. Boos from the Mario series are an example of a major ghost species.
Boos appear in many Mario games, for a complete list of games they appear in, see Boo.