It's still fan fiction even if you run the show

J.K Rowling almost appeared on Doctor Who. [Link]

If Doctor Who's head writer Russell T. Davies had had his way, the next episode of the time-travel action-comedy would have starred Harry Potter author J.K. Rowling. Not only that, but Rowling would have dragged David Tennant's Doctor into the Potter universe.

Doctor Who Harry Potter crossover fic. There are not words.