The repercussions from 'Doctor Who's' 50th anniversary special, the Day of the Doctor, means that next month's Christmas episode could signal the debut of Peter Capaldi's 14th, not 12th, Doctor.
The BBC have referred to Capaldi as the 12th Doctor even since he was announced as Matt Smith's replacement, but the ending of Saturday's show has indicated that this might not actually be the case.
The conclusion of the Day of the Doctor made a reference to all thirteen versions of the character, which included John Hurt's War Doctor who redeemed himself alongside the others after they saved their home planet of Gallifrey from the Time War.
Now Whovians have started to speculate whether Hurt now counts as the 9th Doctor, rather than Christopher Eccleston, who, if Hurt does, would turn into the 10th.
However, another factor to consider is that David Tennant used up a regeneration to save himself during Journey's End after a Dalek struck him.
Steven Moffat has now confirmed that Matt Smith was actually the Thirteenth Doctor, and a source close to the show explained to the Mirror, "There have been two David Tennant Doctor Whos technically and with John Hurt playing another Doctor in the film, it basically means he can't regenerate again."
Moffat added, "The 12 regenerations limit is a central part of Doctor Who mythology, science fiction is all about rules, you can't just casually break them."
He then teased, "So if the Doctor can never change again, what's Peter Capaldi doing in the Christmas special?"
The insider also concluded, "The riddle of the regeneration problem, something fans have talked about for decades, will be faced head on at Christmas. There is going to be another huge cliffhanger and somehow Peter Capaldi has to join and the series has to continue."
There's no doubt that Moffat will face the wrath of some Whovians as he looks to rebuild 'Doctor Who's' mythology at Christmas in order for Capaldi to continue in the role. However, his work on the Day of the Doctor means that he should be allowed a fair whack at attempting to rebuild the beloved character's back story. I doubt that it will work out that way though.
Meanwhile, Moffat has also discussed Capaldi's first full scene as the Doctor, teasing that he "leaps around the place in "post-regeneration madness."
We'll just have to wait to see if we get just a glimpse of Capaldi's first moments as the Time Lord next month, or if we'll see the entire scene that Moffat described.
Are you excited for Peter Capaldi's debut as the Doctor? Will you miss Matt Smith?
Gregory Wakeman is a Doctor Who buff whose favourite incarnation of the character is Christopher Eccleston's 9th Time Lord. Only because he's northern.