A skeleton/person who's gone fucking insane and summons their two beloved dead friends.
But it's mostly Papyrus.
And they also might have a Twitter account that goes by @FishwithBones.
Friend 1: What the hell are you doing!?
Friend 2: IM FUCKING BACKBONE PAPYRUS'ING!
Friend 1: The hell is that!?
Friend 2: YOU DON'T KNOW!?
Friend 1: OF COURSE I DON'T!