Matt Smith has said that he wants to current Doctor to star along-side past Doctor's for the 50th anniversary in 2013.

Recently, John Barrowman and David Tennant have expressed their interest in returning to the show for 2013, but Christopher Eccelston has expressed the total opposite saying he wouldn't "bath in the same river twice".

Matt smith said:
"That's still over a year away but I'd love for it to happen, how amazing would it be to see Tom Baker [back as the Fourth Doctor]? Can you imagine just seeing him back in the scarf, man? That would be amazing.
Paul McGann is a great actor, man, and a great Doctor. I say bring back Chris [Eccleston] and Dave [Tennant], too! How many Doctors can we get into one story? Imagine if there were five or six of us in one ep and we could all just look at each other and judge each other."
In the past, multi-Doctor story have marked the show's big birthday's, with The Three Doctors, The Five Doctors and The Two Doctors. 

Do you want a multi-Doctor episode?