I played though Undertale, and listened to the soundtrack. There is one song on the soundtrack that I didn't recognise from the game. So where does "Song That Might Play When You Fight Sans" appear in the game?
Undertale – Where ‘Song That Might Play When You Fight Sans’ Appears
undertale
Best Answer
Song That Might Play When You Fight Sans is a red herring
The song in question is exclusive to the soundtrack. The song appears nowhere within the game itself, and is intended to throw you off from noticing the real song that plays when you fight Sans:
As a side note, some mods or fangames have been created that show what a comically simple Pacifist run Sans fight would be like, some of which utilize the song as the battle music for said fight.