There's probably some fan fiction out there which focuses on Penny Parker. Maybe she has some kind of relationship with one of the female employees of the Phoenix Foundation. That's the point about fan fiction. People can pick and choose which characters they like best and make all sorts of things happen and they don't have to please anyone else.
That said, I personally couldn't imagine writing fan fiction that wasn't based around
. Unless it was for a totally different programme, and even then there might be some kind of crossover.