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
The Doctor (Doctor Who) kisses Rose Tyler to get the time vortex energy that was killing her back into the TARDIS, subsequently "killing" him and causing his next regeneration. In the New Series Adventures novel "Only Human" by Gareth Roberts, Rose asks the Doctor how he would know that marrying for love is overrated, to which he cryptically answers, "Who says I don't? You ask the Lady Mary Wortley Montagu." In a December 2005 interview on BBC Four, actor David Tennant, who had just taken the role of the Tenth Doctor, described the relationship between the Doctor and Rose as "basically a love story