The Doctor (Doctor Who) Time Lords a fixed number of twelve regenerations, meaning that every Time Lord had a total of thirteen incarnations including the original. The plot of "The Time of the Doctor" involves the Doctor receiving a new cycle of regenerations from the Time Lords before his expected demise, triggering the regeneration into the Twelfth Doctor, played by Peter Capaldi. The origins of the programme were explored in the docudrama "An Adventure in Space and Time" as part of the 50th anniversary celebrations of "Doctor Who", which starred David Bradley as William Hartnell. Although Time Lords resemble humans, their physiology differs in
Space and Time (Doctor Who) canonical. The canonicity of the two mini-episodes was affirmed by Moffat in "Doctor Who Magazine". Moffat stated that, unlike "The Curse of Fatal Death", "Space" and "Time" is not a spoof or a sketch, but rather "a little miniature story" in the style of the "Children in Need" mini-episodes. He described it as "A moment of life aboard the TARDIS. But obviously life about the TARDIS instantly gets you into terrible jeopardy, and all of causality is threatened. As I'm sure it is every day when they get up and have their coffee..." The concept of a TARDIS inside the