‘Doctor Who’ 50th Anniversary: Steven Moffat Redefines The Order of Matt Smith’s Doctor

Spoilers ahead for this year’s “Doctor Who” Christmas special, “The Time of The Doctor!”

During the original “Doctor Who” TV series, it was established that the Doctor can only regenerate 12 times. Prior to the introduction of John Hurt as the War Doctor in “The Name of The Doctor” and “The Day of The Doctor,” Matt Smith’s Doctor was thought to be the Eleventh incarnation of the iconic character.
However, “Doctor Who” showrunner Steven Moffat has pointed out that the Doctor has already regenerated 12 times, making Smith the last Doctor… in theory. 
While speaking with the Daily Mirror, Moffat recalled that David Tennant’s Tenth Doctor used a regeneration to survive his wounds in “Journey’s End,” the fourth season finale. At the time, no one expected that to count as a regeneration because Tennant wasn’t recast as a new Doctor.
“The 12 regenerations limit is a central part of Doctor Who mythology,” noted Moffat. “Science fiction is all about rules, you can’t just casually break them.”
Moffat added that “if the Doctor can never change again, what’s Peter Capaldi doing in the Christmas special?” Capaldi made a brief cameo in “The Day of The Doctor” as the Twelfth Doctor. Or the Thirteenth Doctor, if John Hurt’s War Doctor is now retroactively the Ninth Doctor. Capaldi will officially make his debut as the Doctor in “The Time of The Doctor.”
During a separate interview with Digital Spy, Moffat explained why he allowed the Doctors to save their home world, Gallifrey from destruction in the Time War. 
“It was about a year ago,” recalled Moffat. “I remember thinking, ‘What occasion in the Doctor’s life is the most important?’ – well, it’s the day he blew up Gallifrey. Then I tried to imagine what writing that scene would be like and I thought, ‘There’s kids on Gallifrey and he’s going to push the button? He wouldn’t!’ I don’t care what’s at stake, he’s not going to do it.”
“Of course he never did that,” continued Moffat. “He couldn’t. He’s the Doctor – he’s the man who doesn’t do that. He’s defined by the fact that he doesn’t do that, whatever the cost, he will find another way.”
Regarding the Doctor’s new mission statement at the end of “The Day of The Doctor,” Moffat said that “he has the possibility of going home – he can find Gallifrey – but it might take him a while, who knows? And who knows what he’ll do when he gets there? Get bored and run away again, I would think!”
“It’s not like we’ll spend every episode saying, ‘I nearly found it!’ – we absolutely will not do that – but it gives him somewhere to go,” related Moffat. “The Doctor doesn’t know he’s a character in a television show – he doesn’t know he’s having adventures for our entertainment – he’s got to have something to do and that will be the thing he does.”