Boo is one of the most recognisable enemies in the Super Mario series, a shy ghost that moves only when Mario is not looking at it. The character has appeared across decades of Mario platformers, spin-offs, and animated appearances, which helped its giggling laugh become instantly familiar to gamers. Online, the short laugh is reused in gameplay edits, reaction videos, and Halloween-themed memes, where it instantly signals a ghostly prank without needing any context. Its lasting appeal comes from that mix of nostalgia, humour, and light spookiness.