Megalovania was composed by Toby Fox for Undertale, released in 2015, where it plays during the final boss battle against Sans in the game's Genocide Route. The track had earlier roots in Fox's work on the EarthBound Halloween Hack, but it became famous through Undertale itself. From there it spread through YouTube remixes, speedrun videos, TikTok edits and meme culture, becoming shorthand for an epic or absurd confrontation. Its staying power comes from that instant recognition and its use far beyond the game.