And no, not just whoever he'll be turning into when he regenerates in this year's Christmas special. We're talking about a familiar face from Doctor Who past, who could team up with the Twelfth Doctor for one final trip.
Switch your sonic screwdrivers to their most sceptical setting, as this rumour comes from British tabloid The Mirror — but the newspaper alleges that, in the wake of a supposed departure from latest companion Bill Potts at the end of the now-airing 10th season, the First Doctor himself could reappear alongside his Twelfth incarnation this Christmas. Obviously, with original actor William Hartnell long deceased, the First Doctor would be played by another actor. According to The Mirror that would be none other than Game of Thrones actor David Bradley, who played both Hartnell and the First Doctor to perfection in scenes for the emotional 50th anniversary biopic An Adventure in Space and Time.
The Mirror further alleges that the plot of the Christmas special will link back to the 50th Anniversary of Doctor Who in ways other than just Bradley's reappearance: The special itself will go back to the moment of Capaldi's very first appearance as the Twelfth Doctor in "The Day of the Doctor", and task his final mission as helping to save Gallifrey from destruction in the Time War, alongside his fellow Doctors.
Now, like I said, it's best to treat this firmly as a very wild rumour for now. However, in a lot of ways it makes sense. Both Capaldi and outgoing showrunner Steven Moffat have spoken about a desire to return to that moment Twelve's eyebrows blazed across TV screens within the show's timeline, and as a lifelong Doctor Who fan, Peter Capaldi has long professed his childhood adoration for the earliest era of the show. He's even already getting his dream of fighting the original Cybermen from Hartnell's last story in season 10, so what's to say that an appearance of his childhood Doctor isn't another farewell gift to the actor?
Presumably we'll find out a little more about Doctor Who's Christmas special — and whether or not this rumour holds water — by the end of the season 10 in a few months.