Headcanon that for Christmas dinner Joly insists they all come together for once for a nice dinner at the cafe and that he will cook everything. So during the day before dinner Joly is in the kitchen alone furiously beating eggs with a face mask on so he MAKES SURE no germs get into the food. So whenever someone comes into the kitchen he freaks out and makes them stay at the door unless they thoroughly apply hand sanitizer and put a face mask on. 

So Courfeyrc decided to prank him and come in with wet hands and he pretends sneezes on Joly and the ham and Joly just stops dead, and looks at Courfeyrac traumatized and drops whatever tools he has in his hands and just yells, “COOOOUUURRFEYRACCCC” and everyone else knows what really happened except Joly so everyone is laughing and Joly is just standing there not knowing what is going on shaking from anxiety until Combeferre tells him and he just angrily snaps his mask back over his mouth and stomps into the kitchen slamming the door (which really doesn’t slam it just swing in behind him cause its a kitchen door) and everyone bursts out laughing again.