Eccleston's long refusal to return to Doctor Who on TV has softened a little, with one big exception.
. It also makes sense, especially for an actor who has made clear just how badly his relationship with the production team behindMulti-Doctor stories are fun for us as an audience to get to see the most archetypal versions of these different Doctor incarnations riff off of each other, but that’s by and large the sole appeal of Multi-Doctor specials.
The stories themselves are rarely more than excuses to smash those characters together, and when you’re competing for screen time between huge personalities like the different Doctors are—especially so as a “guest” Doctor next to the current incumbent Time Lord—you’re not really going to get much more deeply into the kind of character exploration you can do than returning to the broadest-sense definition of those past Doctors.