This rip is just the song "Unfounded Revenge" from the game Mother 3. It is not a remix or a mashup of any sort and the advertised track is nowhere in this rip.
There are a few possible explanations for this rip:
- Both "Unfounded Revenge" and "Bonetrousle" are in the key of C minor.
- Unfounded Revenge - Mother 3 does the opposite joke and uses the melody of Bonetrousle.
- Undertale was largely inspired by the Mother series.
- This rip could be a reference to the Sans is Ness meme.
This rip was originally uploaded to the GiIvaSunner channel under the name "Bonetrousle (Unused Beta Mix) - Undertale" on February 29, 2016.