MEGALOVANIA

"MEGALOVANIA" (/ˌmɛ.gʌ.loʊ.ˈveɪ.niː.ə/) is the 100th track in the Undertale Soundtrack. It is a fast-paced song which plays during the final battle against Sans on the Genocide Route.

Origin
"Megalovania" was originally a song composed for Toby Fox's hack of EarthBound titled "The Halloween Hack" which was first seen as a submission to Starmen.Net's 2008 Halloween Funfest. The game itself was an alternate universe of EarthBound where the chosen four never returned or simply put, "bad rom hack with swears", and was used for the game's respective final boss.

This song was later reused in Homestuck as "MeGaLoVania" on the Homestuck Vol. 6: Heir Transparent album where it would make a brief appearance in the Trickster Mode of "[S] Past Karkat: Wake up.", then a full appearance in " [S Wake."] This track's lietmotif can also be heard in the AlterniaBound bonus track, "The Blind Prophet", another track made by Toby Fox.

Trivia

 * The word "Megalovania" is a combination of "Megalomania" and "Transylvania".
 * "Megalomania" is the boss theme from the game Live A Live, which served as an inspiration for "Megalovania". Though Megalovania doesn't directly quote Megalomania's melody, it has a similar feeling and structure. In real life, megalomania is the delusion of being vastly more important and powerful than one really is.
 * The word Transylvania was jammed into the name to give it a feeling reminiscent of Halloween.
 * Toby Fox's mother calls MEGALOVANIA 'MEGALAVEGALA'.
 * "Megalomania" is characterized by arrogance to the point of delusion. It is for this reason that some fans have theorized that "Megalovania" is the theme for the Player/Chara/Frisk, and not Sans, and that instead of the player fighting Sans, Sans is fighting the player. This is supported by the fact that Sans attacks first, dodges every attack, and can perform an off-guard kill on the player once they are convinced into no longer fighting, all of which the player is capable of doing themselves but not other enemies.
 * In addition to "MEGALOVANIA", Sans has his own, unused battle theme: "Song That Might Play When You Fight Sans."
 * According to an interview with Toby Fox, this was one of the six songs originally composed for other projects. The other five were "Fallen Down", "Heartache", "Nyeh Heh Heh!", "Bonetrousle", and "Another Medium".