Pennywise is the shape-shifting clown from Stephen King's IT, first published in 1986 and later brought to screen in the 1990 miniseries and the 2017 and 2019 films, where Bill Skarsgård's performance made the character a modern horror icon. Clips of his laugh and voice have circulated for years in horror compilations and Halloween edits, before becoming a staple sound on TikTok for creepy reveals, clown edits and spooky transitions. Its staying power comes from instant recognition: even without showing the clown, the laugh tells viewers exactly what kind of scare is coming.