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) TARDIS had been previously explored in "The Time Monster" (1972) and "Logopolis" (1980), though both times it was the TARDIS of the Master. Amy also repeats one of her lines from "The Big Bang" at the end of "Space". The special was shot over two days alongside the made-for-DVD "Night and the Doctor" mini-episodes "Bad Night" and "Good Night". It was mostly shot on the first day, where all of the scenes with the TARDIS inside the TARDIS were filmed. Several tricks were used to create the illusion that there were more than one Doctor, Amy, and/or Rory. In scenes