Megalovania was composed by Toby Fox and became famous as Sans's theme in the 2015 role-playing game Undertale, where it plays during the Genocide Route boss fight. The track had earlier versions in other projects, but Undertale made its riff instantly recognisable worldwide. Its relentless energy led to countless remixes, covers and fan animations, and it spread across YouTube and TikTok as shorthand for an unbeatable opponent. It remains popular because a few seconds are enough to set up a dramatic confrontation.