Finn learning about menstruation when Rey and Poe (who is not actually human, and has a hermaphroditic gender) have their cycles sink up. Female Stormtroopers didn’t have periods, they were on medication.

Cue Finn finding out all about it, how to help with the negative symptoms etc, and comforting the two while they all pig out on ice cream and holovids. Others, like Jess, might join them.