The Cast of Undertale's AU Underswap! Undyne was swapped with Alphys, Papyrus with Sans, W.D. with the Riverperson and Napstablook with Mettaton. I didn't completely swap their personalities, because I wanted to keep at least one of their defining traits. Also, the Riverperson was the royal scientist before Undyne in this AU, and Papyrus' late mentor, while W.D. simply left his family. So yeah, that's why he's alive here and the Riverperson is a ghost. #Undertale #Underswap #AlternateUniverse