You Idiot

"You Idiot" is the 78th track in the Undertale Soundtrack. It plays before the fight with Flowey at the end of the Neutral Route, when Flowey traps the main cast with vines before absorbing their souls in the Pacifist Route, and before the "special thanks" segment of the True Pacifist Credits. It sounds like a slow, buzzing, sinister mechanical tune, much like the music that plays when the player meets Chara.

Trivia

 * The song is called 'mus_yourbestfriend_3' in the games files.
 * This hints that there may have been other parts to the song planned, as Your Best Friend is called 'mus_flowey', and there is no mus_yourbestfriend_1 or 2.