Aaaghhh. the only ideas that this gives me is that Charles/whatever James incarnation is this deaf kid who works as a busboy at a restaurant during the afternoons/evenings to make the money needed get himself (and Raven?) through school. Erik/Fassy incarnation goes to this place quite often to hang with his friends on their lunch break or whatever.
Deaf people are almost always very exuberant with facial and physical expressions since they don’t often rely on their voices.
Charles/James never talks much and he’s always really smiley and laughs funny (funny to Erik/Fassy, but its just the common laugh that many deaf people have - a very brusque and loud laugh that they don’t bother trying to stifle since they can’t hear how loud they’re being) so Erik/Fassy just assumes he’s a bit mentally disabled. He thinks this kid is totally adorable - cutest, cheekiest little smarm in the entire world, the way he acts and makes faces and stuff. They flirt, in a way, Erik/Fassy thinks its all in good fun, he wishes the kid could talk but Charles/James always shies away from any conversation Erik/Fassy tries to have.
One day, Erik/Fassy decides ‘fuck it,’ because he’s starting to think that Charles/James is a lot smarter than he seems. He brings a hand up, waves a tip and tries to get Charles/James to come over, but Charles/James is used to being playfully teased by him so he shakes his head a little. Erik/Fassy can’t help but start to smile and mimic the action, so Charles/James does it again with more force.
Only, its just a matter of time before Charles/James’ curiosity gets the best of him and he comes over. Erik/Fassy gives him a dollar for every question he answers - and Charles/James is pretty good at reading lips, but after a while he’d end up getting frustrated and saying in a broken voice, ‘write it down, please?’
and Fassy/Erik realizes that he’s totally gotten the situation wrong the entire time. Charles/James can talk just fine, its only that he can’t hear - not that he can’t understand.