Fresh off the record-breaking Doctor Who 50th Anniversary special “The Day of the Doctor,” Steven Moffat and Co. are trying to find ways to keep the fans occupied until the highly anticipated Christmas special, during which current Doctor Matt Smith will take a bow and turn over the TARDIS to new Doctor Peter Capaldi.

On Sunday, it was revealed on BBC America’s official Facebook page that the episode is called “The Time of the Doctor” (sensing a theme?) and Digital Spy reported Monday that actress Orla Brady (Mistresses and Fringe) will guest star as an old friend of the Doctor’s. No other details about Brady’s role, other than that the plot will revolve largely around her, have been released.

The biggest bomb dropped, though, was Moffat’s weekend announcement during an interview with Radio Times that Matt Smith’s Doctor is in fact the 13th, rather than the 11th. Moffat has officially declared John Hurt’s Doctor as an official incarnation and said that David Tennant’s Doctor used up two regenerations, bringing the tally to 13 lives and leaving fans wondering what this means for the series.

It’s been considered canon since the 1976 episode “The Deadly Assassin” that Time Lords can only regenerate 12 times and live through 13 incarnations, which means Smith should technically be the last Doctor. So where does that leave Capaldi?

Fans had already been theorizing about additional regenerations once John Hurt’s mysterious forgotten Doctor appeared in the season 7 finale, “The Name of the Doctor”, wondering if River Song’s regeneration transfer had something to do with it, or perhaps if when the universe rebooted in “The Big Bang”, so did the Doctor’s regeneration count – or perhaps even the High Council added some regenerations on along the way, as they can do. Obviously Capaldi will still be succeeding Smith as the Doctor — now it’s just a matter of seeing how the regeneration cap-breach is explained in the Christmas special.

Moffat had this to say on the matter:

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.

If science fiction is all about rules, it would appear that Moffat has no plans to break this one. Then again, he also insisted Peter Capaldi wouldn’t be in the 50th Anniversary special — apparently he’s applying the number one rule of the Doctor to himself. Some viewers are already annoyed with him for breaking the First Law of Time and allowing three Doctors to hang out with each other without consequence.

Do you have any theories about who exactly Orla Brady might play, or how Moffat might write his way out of the 12-regeneration rule? Let us know in the comments.

Doctor Who Christmas Special, “The Time of the Doctor,” premieres December 25 on BBC and BBC America.

Sources: Facebook, RadioTimes, Digital Spy