Spookwave

Spookwave is the 39th track in the UNDERTALE Soundtrack. It is one of the 3 CDs that you can play while in Napstablook's house. The song will continue playing after you exit Napstablook's house and if you were to get into an encounter while outside and with this song playing, the enemies will be too spooked to fight you and will run away. Spookwave is a reference to the music genre Vaporwave.

Spookwave also sounds very similar to the theme from the Inspector Gadget Animated Series (1983) when sped up slightly. This could be a reference to how Vaporwave commonly consists of slowed down samples of other songs.