SO with snarky, dirty humor? This happened with my gf the other day and I can't help but wonder how the skelies would react-
(Skeleboi, frustrated): AH FUCK ME!
(SO, straight faced): Maybe later~
My friend does this to me. Also, Vi doesn't swear so it'd have to be, "Ah, frick me!" for him.
Sans- It's really rare Sans swears. It's not his thing, but he'll pull it out every so often. It's probably why he finds your reaction as funny as he does. He'll laugh, and give you this look, but he's amused.
Papyrus- Tells you that now isn't the time! He'll flush a little orange not expecting you to just blurt that out. Papyrus like his brother rarely swears, but boy is it funny when he does so a reaction like that is completely understandable!
Blue- Swears more than you'd think. He'll laugh at your reaction, and then smirk saying why wait?
Stretch- Doesn't swear as much as you'd think. It's just not his thing, but he'll sputter at that cause honestly he never thinks anyone let alone someone like you wants to sleep with him. He sorta forgets that he's an oddly charming dude sometimes.
Edge- Actually laughs. He hadn't expected that, and for some reason this is funny to him. He'll tell you that you got him there, and move on.
Red- Literally swears constantly. He just doesn't care. So, for you to one day just do that, he'll be a bit surprised at first then find it incredibly funny.
Vi- Never swears, but he's got his own "family friendly" versions which he'll bust out all the time. He'll roll his eye lights, but be smiling as he tells you not to make it any worse than it already is. Don't worry, you'll be able to tell that he's obviously teasing.
Money- Roars with laughter, and come to drape himself over you. He's proud. You got him there, and like Blue he's gonna ask why wait? Now seems like a good time too.
Black- Snorts, and like Vi will roll his eye lights, but he finds it amusing. He'll shake his head, and tell you that you're incorrigible.
Wolf- Turns orange as he flushes. Wolf will swear, but usually most of the time people don't hear it. He wasn't expecting for you to hear that, and he's embarrassed.
Bear- Really only swears if he's super frustrated because of his memory, or having a mood swing (or talking to Sans) so he'll probably snap at you. He'll tell you that this isn't funny then stomp off. When he calms down, he'll come back and sheepishly apologize.
Sparrow- He swears more than Papyrus does, but it's usually under his breath when frustrated. So, he'd never expect you to hear, and flush a little that you did. He might leave what's made him frustrated to go spend time with you. That sounds more fun, honestly.
Wine- Laughs loudly. Wine usually swears to prove a point. It's not part of his normal vocabulary since he finds it a little crude at times, but he also thinks swearing can be a little funny. Your reaction to his swear is amusing to him, but he'll also grab you around the waist to pull you against him asking in a low voice, "WHY WAIT?" his gaze hungry.
Coffee- Squeaks in surprise. He didn't mean for you to hear him! He'll pull his hoodie up, and pull the drawstring to hide for a bit. He's pretty flustered, especially coupled with your reaction.