As you relaxed in your very nice house, everything was clean and neat. What you didn't expect was someone to knock on the door. You go over and open the door, it was Alphys. And she seemed to be holding a baby. Looked like...Toriel!?

Alphys: Hey Uh..I sort of messed up pretty badly. As you can see, I accidentally made Toriel into a baby, and I don't know how to care for her. And before you ask, no I can't care for her, my lab is way too dangerous for a baby.