Megalovania was composed by Toby Fox and first appeared in an EarthBound Halloween fan hack before becoming the theme for Sans, the final boss fight in Undertale, released in 2015. Its relentless energy and memorable melody helped it spread far beyond the game through YouTube remixes, covers, speedrun videos and meme edits, where it became shorthand for an impossible or dramatic showdown. Years later it still appears in new edits because listeners recognise it instantly, even if they have never played Undertale.