Doctor Who is a British Sc-Fi Television show that started broadcasting in 1963, it follows the adventures of the "The Doctor" - a Time-Lord from the planet Gallifrey who is able to travel though time in her machine "The Tardis".
Since the shows initial broadcast, it has become a significant part of British popular culture and recently celebrated its 50th Anniversary in 2013 with the special episode "The Day of the Doctor" written by then show runner Steven Moffat.
Eleven Actors have headed the role on screen since William Hartnell's initial incarnation, the current incarnation is played by Jodie Whittaker.
The plot device used to explain the change between actors is officially known as "Regeneration" which allows a critically injured incarnation to renew themselves, it was initially created to allow William Hartnell to step down due to failing health and be replaced by Patrick Troughton and was known as "Renewal", the now official term "Regeneration" was first introduced during Jon Pertwee's Final Serial "Planet of Spiders".
The "Regeneration Cycle" was first introduced in Tom Baker's Serial "The Deadly Assassin" where it was revealed that Time Lords could regenerate 12 times for a total of 13 incarnations, further more details were revealed in Peter Davison's "The Five Doctors" where it was revealed that a Time Lord could been granted multiple cycles allowing further regeneration's - something that was finally used in the Doctor's Case in "The Time of the Doctor".
Incarnations of the Doctor:
- 1st Doctor: William Hartnell (First Incarnation of First Cycle)
- 1st Regeneration - 2nd Doctor: Patrick Troughton (First Regeneration of First Cycle)
- 2nd Regeneration - 3rd Doctor: Jon Pertwee
- 3rd Regeneration - 4th Doctor: Tom Baker
- 4th Regeneration - 5th Doctor: Peter Davison
- 5th Regeneration - 6th Doctor: Colin Baker
- 6th Regeneration - 7th Doctor: Sylvester McCoy
- 7th Regeneration - 8th Doctor: Paul McGann
- 8th Regeneration - War Doctor: John Hurt (A hidden incarnation that appeared in The Day of the Doctor)
- 9th Regeneration - 9th Doctor: Christopher Eccleston
- 10th Regeneration - 10th Doctor: David Tennant (aborted regeneration in The Stolen Earth counts)
- 11th Regeneration - 10th Doctor: David Tennant
- 12th Regeneration - 11th Doctor: Matt Smith (Final Regeneration and Incarnation of First Cycle)
- 12th Doctor: Peter Capaldi (First Incarnation of Second Cycle)
- 1st Regeneration - 13th Doctor: Jodie Whittaker (First Female Incarnation and First Regeneration of Second Cycle)
Incarnations of the Master:
Unlike the Doctor, when the Master first appears he is already on his final regeneration having "wasted" his regeneration cycle. In "The Keeper of Traken" he takes over Tremas body to escape death. By the time of "The Five Doctors" he is offered a new regeneration cycle by "Borusa" on the condition that he saves the Doctor from the Death Zone however they are never received as "Borusa" is revealed to be the villain of the story.
In the TV Movie, the Master is executed by the Daleks and requests the Doctor returns his remains to Gallifrey, however he is able to escape and like Tremas takes over another persons body - this time Bruce.
When the Doctor finally catches up with the Master, he is living as Professor Yana, a human scientist tasked with taking the last of Humanity to "Utopia", he finally discovers who he really is and regenerates and takes on the fake identity of Harold Saxon. In "The Sound of Drums" the Master reveals that he was resurrected by the Time Lords and given a new Regeneration Cycle to fight in the "Time War".
12th Regeneration: 13th Master: Roger Delgado (Final Regeneration of First Cycle)
Peter Pratt and Geoffrey Beevers (Final Incarnation of First Cycle)
Between First and Second Cycle
1.Anthony Ainley (Not a regeneration, transferred his essence into Tremas)
2.Eric Roberts (Again not a regeneration, executed by the Daleks into a Snake-like form - took control of Bruce)
1. Derek Jacobi (Frist Incarnation of Second Cycle)
2. John Simm (Frist Regeneration of Second Cycle)
3. Michelle Gomez (First Female Incarnation)
4. Sacha Dhawan