UNDERSWAP

Underswap is an AU where all of the characters' roles are swapped, as well as their personalities, though some quirks tend to stick in places, or are modified. Sans is the excitable, confident, extremely optimistic human hunter, while Papyrus is the laid back, protective bro following Chara (who is swapped with Frisk). Other swaps in this AU are Asgore and Toriel, Alphys and Undyne, Napstablook and Mettaton, Grillby and Muffet, Burgerpants and Nice Cream Guy, and Flowey and Temmie.

The plot of Underswap revolves around each character from the Undertale universe being swapped with other characters, such as Sans' and Papyrus’ personalities being swapped (although they keep the same names, so what we consider Sans to be as a character is now how Papyrus is, for example). All of the songs are remixed to swapped characters as well.

Canon ChangesSans is swapped with Papyrus.Alphys is swapped with Undyne.Toriel is swapped with Asgore.Grillby is swapped with Muffet.Mettaton is swapped with Napstablook.Flowey is swapped with Temmie.Frisk is swapped with Chara.Burgerpants is swapped with Nice Cream Guy.Non-Canon ChangesTemmie is swapped with Asriel.Aaron is swapped with Shyren.Monster Kid is swapped with Asriel.Mad Dummy is swapped with their cousin, Dummy.Bratty and Catty are swapped with RG 01 and 02.The Annoying Dog remains the same, except... Toby is swapped with Morty.W. D. Gaster is swapped with River Person.Monster Kid is swapped with W. D. Gaster.W. D. Gaster is swapped with Gerson.Asriel is swapped with Chara.Temmie is swapped with Annoying Dog.So Sorry is swapped with Glyde.Froggit is swapped with Whimsun.