Underturn is a Switch Up AU including Scora (an OC).
- Muffet is a soulless purple flower. She sends "Friendliness Spiders", which are actually harmful bullets.
- Scora is the caretaker of the RUINs.
- Asgore hangs out in the RUINs, it's unknown if Scora knows he's there. He also wears a sheet.
- Napstablook is the laidback cousin of Mettaton.
- Mettaton just wants to capture a human so he can join the Royal Guard.
- Riolu wants to see his hero, Asriel, in action.
- Asriel pursues the protagonist throughout Waterfall.
- Chara is the Royal Scientist.
- Toriel is the star of the Underground.
- Undyne was the Royal Scientist before Chara.
- Temmie is an employee at TRL Resort. She hates her life.
- Grillby is the king of the Underground and the ex-husband of Scora.
- Sans was the older brother of Papyrus before he died. Chara managed to bring him back, as a flower.
- Papyrus possesses Frisk during the Genocide Run.
- MK runs a secret shop. You can pay for his college Education, and he will let you buy MK Armour.
- Gaster runs a diner in Snowdin. He gets very angry if his number one customer, Napstablook, is killed. He sells Burgers and Fries.
- Alphys runs a sale in Hotland. She sells Instant Noodles. She will get very angry if the protagonist doesn't buy from it, although purchasing something costs 9999 gold.