In a new interview with Doctor Who's Steven Moffat, released Friday on YouTube and embedded below, the showrunner addresses one of the things that's been nagging at some Who viewers since the recent announcement that former Doctor Who and Torchwood guest star Peter Capaldi would appear as the next iteration of the Doctor, beginning with this year's Christmas Special when Matt Smith leaves the show. "We are aware that Peter Capaldi's played a big part in Doctor Who before and we're not going to ignore the fact, and Torchwood," Moffat said. "I'll let you in on this. I remember Russell [T. Davies] told me he had a big old plan as to why there were two Peter Capaldis in the Who universe, one in Pompeii and one in Torchwood. When I cast Peter and [Russell] got in touch to say how pleased he was I said, 'Okay, what was your theory and does it still work?' He said 'Yes it does, here it is.' So I don't know if we'll get to it. We'll play that one out over time. It's actually quite neat." The Doctor Who Fiftieth Anniversary Special is set to air on November 23, followed shortly thereafter by the Christmas Special, which will be Capaldi's first appearance as The Doctor.