In an interview with Times Online, Doctor Who Executive Producer/Writer Russell T. Davies has stated he would have loved to have done a Doctor Who and Star Trek crossover.
I would have loved to have done a Star Trek crossover. The very first year, we talked about it. Then Star Trek finally went off air. Landing the Tardis on board the Enterprise would have been magnificent. Can you imagine what their script department would have wanted, and what I would have wanted? It would have been the biggest battle.
The interview then moves on from Star Trek to Star Wars, with Davies being asked whether or not Geoge Lucas asked him to participate in his new live-action Star Wars series.
He came knocking on every single writer’s door in the whole land. And there are British writers working for him on this Star Wars series. But I’m not allowed to say who. The writers are out there now, at Skywalker Ranch (in California). Yesterday, they were allowed into the props room; they were playing with lightsabers. It’s a lovely job. But I’m not going to do a sci-fi series that’s second-rate compared to Doctor Who (hoots of laughter).
He was also asked how much influence he would exert over Matt Smith’s version of Doctor Who:
Absolutely none. I wouldn’t want to write a single word for him. When he appears, every word will be written by Steven Moffat. He’s Steven’s, and Matt’s, character.