Megalovania was composed by Toby Fox and is best known as the theme for Sans, the final boss of the genocide route in Undertale, released in 2015. An earlier version appeared in Fox's EarthBound Halloween Hack, but the Undertale version became the famous one, spreading through Let's Plays, remixes and fan videos. Its relentless rhythm and instantly recognisable melody made it a shorthand for an unbeatable opponent, and creators still reuse the drop to signal a sudden shift in power, confidence or chaos.