(It’s all good, friend! I’ve just been gone, lol. Also... how did you fall asleep on someone’s butt?)
Swapfell Sans:
Confused. And most likely pissed. I mean what the fuck kind of joke is that? He’s honestly offended. He’s certain you’re telling the joke in front of him in order to make him jealous so that he will come to you and confess. That must be it. Why else would you talk about someone’s butt and not his? Unless you are talking about his butt, and he’s just not present when you do. In that case, he understands your joke. You’re just shy and want to confess to him. However, you aren’t terrific at social cues like he is. So you don’t know that this “joke” is the wrong way to tell him that you are head-over-heels-completely-and-totally-in-love with him. But don’t worry. He is prepared to prove to you that you can tell him. By talking about sleeping on other people’s butts in front of you. That will show you!
Swapfell Papyrus:
Panic. Pure panic. Then depression. Oh dear... He knew it was too good to be true. This crush, he means. You’re obviously in love with this friend of yours. Like... why would he even think he had a chance. Damn..! You won’t see him for a while after this, because he’s now avoiding you in order to save his emotions. On top of that, he’s convinced you may have known about his crush on you and decided that you were going to hint that you didn’t like him with this. He’s also spending this time trying to convince Sans not to attack you.
Underswap Sans:
Stop! What are you doing?! That’s inappropriate! You shouldn’t be discussing.... b-bottoms! He’s mortified. But that doesn’t make him like you any less. He also isn’t too discrete about his crush on you. You’re more than likely are aware. You are also more than likely aware of his disapproval of the joke by his polite-repulsion every time you make the inside joke. Rather than feeling offended about this joke being told to another person, he’s more concerned about the joke itself. He has more than enough self-confidence to assure himself that, while the joke is highly disagreeable, this inside joke is told with innocent intentions.
Underswap Papyrus:
Uh... Wat. I mean... okay? Heh... He doesn’t mind the joke, he says. It’s all in good fun. And he doesn’t mind that it’s a joke with a friend. No, really, he’s not jealous. It’s more just... uncomfortable. He says absolutely nothing, however. He’ll be damned if he spoils the fun. He’ll just have to make some inside jokes with you too.