the only AU i know of that casts chara as undyne is taletwist but that's getting rebooted and the characters might not be in the same roles so for now this has no specific AU
i don't really consider beta undertale a cha…
shuffleshift..?
( I thought you didn't use msb? )
Spinspin? Taletwist?
This is really catchy and i get some Shantae vibes from this