The Doctor

The Doctor is a Time Lord from the planet Gallifrey, who wanders through time and space in his ship, the TARDIS. For the most part, and usually because the vessel's navigation system is old and unreliable, he explores the universe at random and uses his extensive knowledge of science and advanced technology to heroically avert the crises that he encounters. The Doctor has, at various times, been accompanied by companions who have chosen to travel with him for a variety of reasons.

The Doctor is considered a renegade by his fellow Time Lords, for his penchant of getting "involved" with the affairs of other worlds, in direct violation of official Time Lord policy. However, most of the time his actions are tolerated, especially when he has saved not just Gallifrey, but the universe, several times over. His standing in Time Lord society has waxed and waned over the years, from being a hunted man to even being appointed Lord President of the High Council (an office he did not assume for very long and eventually was removed from in his absence). In the end, though, he has always seemed quite content to remain a renegade and an exile.

Changing faces
To date, the Doctor has gone through nine of his allotted twelve regenerations, and so is currently in his tenth incarnation. Most of his regenerations have been the result of some mortal injury, although his second was forced upon him prior to his exile to 20th century Earth by the Time Lords. His first was due to old age, although radiation from an Earth weapon known as the Z-Bomb may have also played a factor.

Despite the fact that the Doctor is supposed to be the same person throughout his regenerations, each one has been imbued with his own distinct quirks and characteristics. At his core, however, the Doctor continues to be a heroic figure, fighting the evils of the universe wherever he finds them, even if his values and motives are sometimes alien.

The Ten Doctors

 * The First Doctor was an irascible, grandfatherly type, a brilliant but often short-tempered scientist.


 * The Second Doctor was a sort of "cosmic hobo," often frightened of the alien menaces he faced, whose solutions were sometimes of a hit-or-miss nature.


 * The Third Doctor cut more of a dashing figure than his predecessors, a dandy with a penchant for gadgets and martial arts, particularly Venusian akido.


 * The Fourth Doctor was something of a cross between Willy Wonka and the Mad Hatter, rarely without his signature scarf of incredible length. He was perhaps the most eccentric incarnation.


 * The Fifth Doctor had a fondness for cricket. He was somewhat more nervous and less sure of himself than the two previous Doctors, though no less heroic.


 * The Sixth Doctor, sporting a multi-hued wardrobe that looked as if designed by Christian Lacroix, had a manic personality and an ascerbic wit.


 * The Seventh Doctor, his voice touched by a Scottish burr, combined the vagabound nature of the Second and Fourth Doctors with the scientific brilliance of the First and Third incarnations.


 * The Eighth Doctor showed a romantic and sensitive side not evident in the previous Doctors. This Doctor suffered bouts of amnesia, first after his initial regeneration and again after the destruction of Gallifrey ("The Eight Doctors," "Ancestor Cell").


 * The Ninth Doctor displays much of the playfulness of the Fourth and Seventh Doctors, but also displays a pragmatism which can at times appear callous. This Doctor also seems more consciously aware of the effects his actions have on those around him. His attire is also considerably more conservative and less conspicuous than those of his predecessors.


 * The Tenth Doctor's character is that of an eccentric crackpot, a cross between the Fourth Doctor and the Ninth. He has a serious side, but quite often his other wins out. He occasionally has a dark edge to his character.

Other Doctors
Due to the fluid nature of the time-stream and the existence of parallel realities, other versions of the Doctor have come to light. Following are descriptions of some of those currently known to exist.

Past Doctors

 * During a mental battle between the Doctor and the Time Lord war criminal Morbius a visual display indicated that the Doctor had at least eight incarnations prior to the First Doctor. However, this would contradict the limitation of Time Lords to twelve regenerations (see next point below), particularly as there have been five more Doctors since this event occurred, and upon their initial meeting in the Death Zone, the Fifth Doctor clearly identified himself to the First Doctor as being the result of a fourth regeneration. Theories abound to explain this curious phenomenon, including ones that the images were of Morbius's previous incarnations or that they were false images induced by the Doctor. Events on Gallifrey which occurred shortly before the end of the Seventh Doctor's life  suggest that these were actually the Doctor's incarnations during his previous existence on Gallifrey as "the Other," the legendary and mysterious third collaborator with Rassilon and Omega in the experiments which led to the founding of Time Lord civilization("The Brain of Morbius", "Lungbarrow)."


 * Time Lords are not necessarily limited to twelve regenerations. In "The Five Doctors", Borusa offered the Master "regeneration: a complete new life cycle" for his help.  This may mean that Time Lords have ways to extend the regeneration cycle.

Future Doctors

 * During his last battle with the Master, the Fourth Doctor was assisted by a mysterious white-garbed figure known as the Watcher who also assisted in the transition between the Fourth and Fifth Doctors. Nyssa commented that the Watcher "was the Doctor all the time." This apparent paradox of the intermittent stage between incarnations showing up before the events which triggered the Doctor's regeneration was perhaps created by the Master's sabotage of the operations of Logopolis, which the Monitor warned was interfering with the law of cause and effect. In other words, the effect of the Doctor's regeneration, represented by the Watcher, was showing up before its cause, the Fourth Doctor's fall from the Pharos Project dish tower (Logopolis).
 * The prologue of Battlfield features a future doctor known as Merlin, who first appeared in the comic strips The neutron knights and The tides of time, and later appeared in short stories and novels.

Third Doctor

 * During his trial the Second Doctor was shown a series of portraits from which he might choose the form of his next regeneration before the Time Lords exiled him to Earth. None was to his liking, nor did any of them look like theThird Doctor. The existence of these "could-have-been" Doctors in alternate realities are possible ("The War Games)."


 * An Unbound Third Doctor who never joined UNIT as its scientific advisor, but instead met and befriended the Brigadier long after his UNIT heyday, is also known to exist. ("Sympathy for the Devil").


 * The machinations of Faction Paradox created an earlier death on the planet Dust for the Third Doctor than had occurred in the Doctor's established timeline. He still regenerated into the same Fourth Doctor, and almost everything else remained the same, but it created a paradox which left the Eighth Doctor susceptible to Faction Paradox's plans ("Interference").

Fourth Doctor

 * Having just regenerated, the Alternative Fourth Doctor and his new companions Jenny and Jimmy prevented the Daleks from gaining the Crystal of All Power. (The Seven Keys to Doomsday.)

Sixth Doctor

 * The Seventh Doctor encountered a Land of Fiction version of the Sixth Doctor, who blamed his sucessor for regenerating prematurely ("Head Games").

Seventh Doctor

 * During a visit to Britain in 2001, the Seventh Doctor faced off with Dr. Who, his evil duplicate from the Land of Fiction.

Ninth Doctor

 * A melancholic Alternative Ninth Doctor, at first reluctantly, fought the Shalka on Earth, and in so doing acquiring a new travelling companion, Alison Cheney.

Other Versions or Incarnations

 * During the Doctor's second trial, a Time Lord with the title of the Valeyard was revealed to be a potential future Doctor, existing somewhere between his twelfth and final incarnations and embodying all the evil and malevolence of the Doctor's dark side. The Valeyard was defeated in his attempt to actualize himself by stealing the Sixth Doctor's remaining regenerations, however, and so may never actually come to exist ("The Trial of a Time Lord").


 * During his adventure in the "Inferno" universe, the Doctor saw a poster of the leader of that reality's version of Britain, a fascist military dictator. Though not known at the time, this was later revealed to actually be that reality's version of the Doctor. This alternate universe also features a more benevolent version of the Master ("Inferno", "Face of the Enemy") .


 * An Unbound Doctor who never left Gallifrey. "(Auld Mortality)." 


 * An Unbound Doctor who changed Earth history, with disastrous results "(A Storm of Angels)".


 * An Unbound Doctor who, while not really evil, is nonetheless far from heroic. This Doctor believes that the ends justify the means. "(Full Fathom Five)".


 * An alternate reality version of the Valeyard who won his battle with the Sixth Doctor in the Unbound story "(He Jests at Scars...)". 


 * An Unbound Doctor who turns out to be the fantasy world alter ego of a mentally ill writer recollecting his script for a proposed television series about a character tentatively called "Doctor Who" (Deadline).


 * An Unbound boozy female Doctor who has escaped punishment by the Time Lords ("The War Games"). This story also features appearances by her past male Unbound incarnation. ("Exile".)


 * The Wanderer is somewhat similar to the Doctor.