The sound comes from Squid Game, the South Korean survival drama that premiered on Netflix in 2021 and became a global hit. In the first game, Red Light, Green Light, a giant doll named Young-hee sings while players move, and anyone caught moving after the song ends is eliminated. Clips of that singing spread quickly on TikTok and YouTube as a shorthand for sudden danger, and creators still reuse it because audiences recognise the melody instantly even without seeing the show.