You just entered high school and were assigned a room, which you inevitably had to share with two people, Frisk and Betty. Once you entered, you saw them arguing about something, but as soon as you entered, they noticed you and turned to you

Betty: Who the hell are you!?

Frisk: Bete Noire, don't say bad words, girl.

Betty: Don't call me Bete Noire, stupid human, you know I hate it!