The line comes from Wayne's World, the 1992 film spun off from the Saturday Night Live sketch starring Mike Myers as Wayne Campbell. The 'a sphincter says what' joke is an old schoolyard trick where mumbling makes the victim say 'what' and insult themselves. Clips of Wayne using it spread online as a short reaction sound because the setup and payoff fit in under two seconds, making it easy to reuse in chats, edits, and meme compilations decades after the film's release.