There’s no way that Matt Smith’s 11th Doctor would retroactively replace Peter Capaldi’s 12th Doctor in a reverse regeneration scenario, but there could be all sorts of other interesting, and legitimate ways for him to return to the current timeline of Doctor Who.
In a recent interview with EW Matt Smith compared the alienation of his newest character, Prince Philip on Netflix’s The Crown, to his tenure as the 11th Doctor. Ever the fan favorite among Whovians, Smith denied rumors that he’s been asked to return Doctor Who right away, but he did confirm he totally would if asked.
“I would consider any approach and take it very seriously,” Smith said.
So, if there were a “serious” approach, how might the time-traveling show incorporate the return of that Doctor’s face?
The 11th incarnation of the Doctor is very much so dead, so it’s not like he’ll magically just be alive again (remember they already played that card with the Teselecta in “The Wedding of River Song”). In “The Time of the Doctor,” the 11th Doctor spent 300 years protecting a town called Christmas from all manner of invasions from past enemies. It was then that we learned that a Time Lord’s regenerations were limited to a cycle of 12. (The 10th Doctor’s vanity used up two … charges?) The Doctor spent what he thought was his last life protecting the town only to have Clara negotiate a fresh cycle of Regenerations from Gallifrey.
Remember, we did see two “dead” Doctors reunite with the then-current 11th Doctor in the 50th anniversary — “The Day of the Doctor” — to save the War Doctor from himself and save the Earth from a Zygon invasion (in fact, ALL thirteen Doctors technically participated in the ensuing craziness).
We also saw at the very end of the episode (pictured below), the familiar face of Tom Baker who sort of was reprising his role as the 4th Doctor (you know, the one with the crazy scarf).
There are many precedents for multiple Doctors being in a storyline together — even in TV — making it almost certain that the 11th Doctor will make an appearance on the show again at some point for some sort of anniversary special. The 11th Doctor lived for about hundreds of years wearing that face and bowtie, so it stands to reason that might see him at a previously unseen point during that time.
But the face could return in other ways too. Hologram recordings in the TARDIS data files. Weird clones. Memories. Flashbacks. Who’s to say that you can’t go back to the same face considering it’s a “fresh” cycle? Even if it was a one-off episode in which they burned through two regenerations just to feature Matt Smith again, it could make for interesting plot.
Also recall that Smith has already reprised the role post-mortem in Capaldi’s first episode, calling Clara from the past. Though it would tire quickly to do this again, they could have the 11th Doctor phone in a warning of some kind.
During Capaldi’s time as the 12th Doctor, we came to learn that there’s some method to the madness of how the Doctor receives his new faces. He chose the Capaldi-face to remind himself of the Roman man he saved in “Fires of Pompeii” as a way to remember that the Doctor is supposed to save people.
Ultimately, Matt Smith speaks with wistful regret about leaving the show so soon. Maybe, if we’re all lucky, immortal Clara might go back with her Diner-TARDIS and find the Doctor she originally fell for, if only for one episode spent comparing who has the better “Snogbox.”