King Boo is the leader of the Boos in Nintendo's Mario universe and the main antagonist of Luigi's Mansion, where Luigi must capture ghosts haunting a mansion. His distinctive laugh became closely tied to the character as players encountered him throughout the games, and clips of it spread through gaming videos, memes and soundboards. It remains popular because it is instantly recognisable, cartoonishly sinister and short enough to drop into edits, streams and Halloween content without needing any explanation.