Oh, I have an idea for your fake dating prompt: most of the time the two people who are fake dating are the ones who end up together, but what if you set it up so that one of them is in an established relationship with somebody else, and for plot reasons has to fake date this other person? So if you wrote this for Teen Wolf, Stiles could be investigating something werewolfy, and for *handwave* reasons it wouldn't work for him to show up with Derek, so he goes undercover by fake dating Erica (or whomever).