The Day of the Doctor” turned out to be serious, too. It revolved around the use of a genocidal weapon by the Time Lords—possibly, even, by the Doctor himself—against their mortal enemies, the Daleks, a race of fascist maniacs whose rallying cry is “Exterminate!” This weapon, we were told, was so powerful that it had become self-aware. “How do you use a weapon of ultimate mass destruction,” one character asks, “when it can pass judgment on you?” The room was silent—not a single sonic screwdriver whirred. That’s the genius of “Doctor Who”: in it, silliness and seriousness, death and vitality, the ludicrous and the real are all squeezed together. It’s bigger on the inside than it is on the outside.
John Hurt’s Doctor doesn’t use the title, therefore he’s in his 12th body but [Matt Smith is] the Eleventh Doctor. However, there is no such character and never has been as the Eleventh Doctor. He’s just the Doctor, that’s what he calls himself. The numbering doesn’t matter. So I’ve given you the option of not counting [Hurt] numerically as the War Doctor. He’s used up another regeneration, so I expect he’ll be in trouble shortly.
Steven Moffat on ‘Doctor numbers’ | Articles | Doctor Who (via doctorwho)