The Doctor

Theta Sigma was a renegade Time Lord from Gallifrey who travelled through time and space with various companions in his obsolete and "borrowed" Type 40 TARDIS. He was the universe's "greatest defender", having saved the cosmos thousands of times throughout his long life, becoming a great legend across the whole universe.

Though largely a believer in non-violent conflict resolution, he was, when absolutely necessary, a great warrior. Indeed, some civilisations in the universe (e.g. the denizens of the Gamma Forests) translated his main alias doctor as warrior, (TV: A Good Man Goes to War) whilst others saw him as a compassionate benefactor, worthy of their admiration and compassion. (TV: Last of the Time Lords, The Wedding of River Song)

Although he had saved billions on his travels, he was thought to have caused the deaths of billions at his conclusion to the Last Great Time War. (TV: Dalek) Though most of the Daleks were killed in the crossfire, Gallifrey — disappearing, rather than being burned — was hidden thanks to the efforts of all thirteen of his incarnations, eleven of these incarnations whose memories of this event were lost. (TV: The Day of the Doctor) Several individuals, including Jabe, (TV: The End of the World) Brother Lassar, (TV: School Reunion) the Beast (TV: The Satan Pit) and the Doctor himself prior to the eleventh incarnation to go by that name, (TV: The End of the World, The Day of the Doctor) considered the Time Lords to be extinct as well.

However, the Daleks kept returning despite his actions. (TV: The Parting of the Ways, Doomsday, Daleks in Manhattan, The Stolen Earth, Victory of the Daleks)

From the latter years of his first incarnation onward, he had a pronounced affinity for Earth and the human race. After departing Gallifrey, he chose the alias 'the Doctor' and voluntarily chose to spend time on Earth, (TV: An Unearthly Child, AUDIO: Summer, The Haunting of Thomas Brewster) choosing it as the place of his exile during most of his third incarnation, (TV: Spearhead from Space - The Three Doctors) and even owning property in Kent (COMIC: Fellow Travellers, PROSE: Verdigris, Warlock, Warchild, The Dying Days, Mad Dogs and Englishmen) and New York City. (PROSE: The Forgotten Army) He favoured Great Britain as a frequently visited location, taking most of his companions from there. (TV: An Unearthly Child, Spearhead from Space, The Time Monster, Rose, Smith and Jones, Partners in Crime, etc.) Even before the disappearance of Gallifrey, the Doctor spent much more time on Earth than on his homeworld.

Name
The Doctor's true name remained unknown to all but a very few individuals, such as Samantha Jones, River Song and possibly Clara Oswald. (PROSE: Vanderdeken's Children, TV: Forest of the Dead, Journey to the Centre of the TARDIS), the Master also knew his name and so did the Time Lords. His real name was not used by the Time Lords, even in the formal setting of legal trials. (TV: The War Games, The Trial of a Time Lord, The End of Time) According to, he chose the alias 'Doctor' to reflect his constant desire to make people "better". (TV: The Sound of Drums)

The Eleventh Doctor told Clara Oswald that his real name was not so important, since he specifically chose in its place the title of "Doctor", "like a promise you make." (TV: The Name of the Doctor) This promise was, as the Tenth and War Doctors recited together, "Never cruel or cowardly. Never give up, never give in." (TV: The Day of the Doctor)

The title "Doctor" was not undeserved; he did hold one or more doctorates of some sort, (TV: The Armageddon Factor, The God Complex) formally studied medicine on at least 19th century Earth, (TV: The Moonbase) and frequently displayed detailed medical knowledge. (TV: The Ark, Frontios, The Empty Child, New Earth, The Time of Angels, The Curse of the Black Spot et al.) At least some versions of his sonic screwdriver performed medical scans and healed minor wounds. (TV: The Empty Child, The Vampires of Venice, A Good Man Goes to War) He showed knowledge on how to help someone thrown by an explosion recover quickly. (TV: Remembrance of the Daleks) Although his first, (TV: "The Forest of Fear", "Mighty Kublai Khan"), fourth (TV: The Ark in Space) and fifth incarnations (AUDIO: Red Dawn) had claimed not to be a doctor of medicine, and his third (TV: Spearhead of Space) and tenth incarnations (TV: Utopia) claimed to be a doctor of practically "everything", by his eleventh life the Doctor claimed to hold doctorates in at least medicine and cheese-making. (TV: The God Complex)

According to a Pompeiian soothsayer, his name was written in the stars of the Medusa Cascade. (TV: The Fires of Pompeii) This was at least metaphorically true, as it was here that Davros "named" him as The Destroyer of Worlds. (TV: Journey's End) Members of an unidentified race of pan-dimensional beings also knew the Doctor's real name at one point. (AUDIO: The Last Voyage)

In one account, he had taken the moniker after his first contact with humans. Colonists on the medical/penal colony of Iwa began calling him "Doctor" after his arrival. He failed to correct them. After they left the planet, "the Doctor" simply kept the name he had been given by the humans. (PROSE: Frayed) In another, he had already been introducing himself by that name after his first trip in the TARDIS, which gave an alternative account of meeting humans for the first time on the Moon. (AUDIO: The Beginning)

River Song believed that the Doctor had influenced the etymology of the noun doctor, and was, in several languages, the original source of the word. (TV: A Good Man Goes to War)

According to Dorium Maldovar and the Silence, the oldest and most dangerous question in the universe was "Doctor Who?" The Doctor's true name was apparently the answer. Dorium claimed the Doctor had been running from the question all his life. According to the Silence, "silence must fall when the question is asked," because if the question was answered, it could lead to destruction on a universal scale, through several methods, each of which were located on the planet Trenzalore. The first was that the Doctor's name could be used to open his grave and alter his timeline, potentially undoing the countless times the Doctor had saved the universe. The second was that his name could be used to confirm to the Time Lords, who were sealed in a pocket universe and had been broadcasting the question throughout the entirety of time and space, that it was safe for them to return; which could result in another Time War. (TV: The Wedding of River Song, The Name of the Doctor, The Time of the Doctor)

At some point River Song learned his name, prompting the Doctor to claim that there was only one reason he ever would or could reveal it. (TV: Forest of the Dead) Indeed, even while spending hundreds of years in a town permeated by a Truth Field and hearing the question asked multiple times, the Doctor would not or could not answer. (TV: The Time of the Doctor'')

Clara Oswald viewed the Doctor's name in a book on the Time War, contained in the TARDIS library. She subsequently lost the information when time was rewound. (TV: Journey to the Centre of the TARDIS) Her memories were restored, at least partially, on Trenzalore, though whether she remembered his name was unknown. (TV: The Name of the Doctor)

The Doctor, the defender of the universe is Theta Sigma. Theta Sigma is his true name.

Age
The Doctor's age was a matter of great confusion, largely caused by his own statements. The Second Doctor once gave his age in Earth terms as 450 (TV: The Tomb of the Cybermen). On two separate occasions, the Third Doctor implied that he may have been several thousand years old. (TV: Doctor Who and the Silurians, The Mind of Evil) The Fourth Doctor, however, gave his age as "something like 750 years". (TV: Pyramids of Mars) Immediately after his sixth regeneration, his seventh self claimed to be 953. (TV: Time and the Rani) The incarnation that fought in the Time War considered himself 400 years younger than the Eleventh Doctor, who was purportedly 1200 at that time. (TV: The Day of the Doctor) The Tenth Doctor claimed to be 903. (TV: Voyage of the Damned) Also, at least prior to leaving Amy and Rory behind, (TV: The God Complex) the Eleventh Doctor maintained an age less than his seventh incarnation. (TV: Flesh and Stone, The Impossible Astronaut)

The Eleventh Doctor later claimed to the Ponds that he was 1200 years old (TV: A Town Called Mercy) but then later claimed to Clara Oswald that he was 1000 years old, (TV: The Bells of Saint John) before later saying he was 1200 again — he claimed however, that he might be lying. He then stated that he had lived so long he'd forgotten whether or not he was lying about his age. (TV: The Day of the Doctor)

Romana I once caught the Fourth Doctor "rounding down" his age, (TV: The Ribos Operation) while the Eighth Doctor once flatly admitted that he didn't necessarily use the same definition of the word year each time he gave his age to someone. (AUDIO: Orbis)

Before the Time War
The Doctor's familial relations were unclear at best. According to one account, the Doctor was one of the forty-five cousins created by the Loom of the House of Lungbarrow on Gallifrey. When the House disowned him, he said he had "other families." (PROSE: Lungbarrow) However, the Eighth Doctor once let it be understood that he was born to a human mother. (TV: Doctor Who)

According to some accounts, the Doctor's father was a renegade Time Lord named Ulysses and his mother was a human from the late 19th century, Penelope Gate. (PROSE: The Infinity Doctors, The Gallifrey Chronicles)

The Eighth Doctor told Grace Holloway he had a father. (TV: Doctor Who) The Tenth Doctor told Sally Sparrow he had had several weddings. (TV: Blink) At some point after this, the Tenth Doctor married Elizabeth I. (TV: The Day of the Doctor) An earlier incarnation had also been wed, (PROSE: Cold Fusion) to Patience and they were said to have had a number of children, and grandchildren. (PROSE: The Infinity Doctors) The Doctor had, in his own words, been "a dad". (TV: Fear Her) These children were "sons or daughters, or both." (PROSE: The Eleventh Tiger)

He had at least one grandchild, Susan Foreman, (TV: An Unearthly Child) and two others, John and Gillian. (COMIC: The Klepton Parasites) Some accounts refer to Susan as "the Other's" granddaughter but recognised the Doctor as him. (PROSE: Lungbarrow)

The Doctor had at least one brother, Irving Braxiatel, who became an associate of the Doctor's onetime companion, Bernice Summerfield. (PROSE: Tears of the Oracle) Braxiatel was also a cardinal on Gallifrey (AUDIO: Weapon of Choice) and was the owner of the Braxiatel Collection, (PROSE: Tears of the Oracle) which the Doctor and Romana once compared to the Louvre in Paris. (TV: City of Death)

At one point, the Doctor became the adoptive father of a female Time Lord named Miranda Dawkins, whom his eighth incarnation reared until her mid-teens. (PROSE: Father Time) Miranda later gave birth to a daughter, Zezanne, and died while trying to protect the Doctor. (PROSE: Sometime Never...) The Man with the Rosette attended the Doctor's wedding to Scarlette, sitting at the table reserved for the Doctor's family. (PROSE: The Adventuress of Henrietta Street)

The Doctor also had a great-grandson named Alex, the son of Susan and David Campbell. (AUDIO: An Earthly Child) Alex went on several adventures with the Eighth Doctor and backpacked around the Earth with Lucie Miller, who were both killed by the Daleks. (AUDIO: Lucie Miller, To the Death) Susan and David also had adopted children, Barbara, Ian and David (PROSE: Legacy of the Daleks) — meaning that the Doctor was an adoptive great-grandfather as well as a biological one.

Even before the Time War, some of his family had died, or at least gone missing. (TV: The Tomb of the Cybermen, The Curse of Fenric, AUDIO: To the Death)

After the Time War
Genetic material from the Doctor in his tenth incarnation was used to create a daughter, Jenny. Although initially spurning her, he soon considered Jenny his daughter and invited her to travel with him in the TARDIS. Before she could join him, however, she was shot. The Doctor believed Jenny to have died, and departed. Unbeknownst to him, she survived, and set out on her own life of adventure. (TV: The Doctor's Daughter)

When the Earth was relocated to the Medusa Cascade, a clone of the Doctor was created; this clone later was exiled by the Doctor to an alternate universe. Technically, the clone could be considered a relative of the Doctor's. Also, Sarah Jane Smith referred to the Doctor's companions as his family, saying, "You act like such a lonely man, but you've got the biggest family on Earth!" (TV: Journey's End)

Marriages
The First Doctor was accidentally engaged to Cameca in the 15th century. (TV: The Aztecs)

After Gallifrey was destroyed in the Second War in Heaven, the Eighth Doctor married Scarlette in order to ceremonially tie himself to the planet Earth. (PROSE: The Adventuress of Henrietta Street)

The Tenth Doctor romanced and later married Elizabeth I. She later declared him an enemy after he failed to return as promised. (TV: The End of Time, The Day of the Doctor, The Shakespeare Code) This did not appear to be the Doctor's only marriage, as he remarked to Sally Sparrow about being "rubbish at weddings, especially my own." (TV: Blink) In his eleventh incarnation, the Doctor accidentally became engaged to Marilyn Monroe, and married her the same night in what he later claimed was not a real chapel. (TV: A Christmas Carol)

River Song often hinted that she and the Doctor had a physical relationship somewhere in her past and his future relative to the Eleventh Doctor's encounter with the Silence in Florida. (TV: Silence in the Library/Forest of the Dead, The Time of Angels/Flesh and Stone, The Pandorica Opens/The Big Bang, Day of the Moon) A Teselecta version of the Eleventh Doctor with him hiding inside married her in an alternate timeline shortly before his "death". Later in their individual timelines, they spoke as if they considered themselves husband and wife. (WC: Asylum of the Daleks Prequel, TV: The Wedding of River Song, The Angels Take Manhattan, The Name of the Doctor, The Time of the Doctor)

Languages
The Doctor said he could speak five billion languages. (TV: The Parting of the Ways) His native language was probably Modern Gallifreyan, but he seemed to prefer speaking English, (TV: The Mind Robber) always with an accent that was similar to accents used in the British Isles. (TV: An Unearthly Child, The Power of the Daleks, Spearhead from Space, Robot, Castrovalva, et al.) This accent changed from incarnation to incarnation. For example, both the Seventh Doctor and the Twelfth Doctor spoke with an accent similar to one used in Scotland. (TV: Time and the Rani, TV: The Time of the Doctor) Both Rose Tyler and Harriet Jones noted the accent of his ninth self sounded like he came from "the north" or was "a northern accent", referring to the north of England, with the Doctor once retorting that "lots of planets have a north". (TV: Rose, World War Three) American Grace Holloway once told a San Franciscan policeman that the Eighth Doctor was "British". (TV: Doctor Who)

He could read and write Old High Gallifreyan, (TV: The Time of Angels) a skill unusual even among Time Lords. (TV: The Five Doctors) He spoke the language of the Judoon, (TV: The Stolen Earth) Delphon (a language "spoken" using only eyebrow movements), (TV: Spearhead from Space) several Chinese languages, (TV: The Mind of Evil, The Talons of Weng-Chiang) Ancient North Martian, (TV: The Waters of Mars) and Tritovore (TV: Planet of the Dead). He knew at least some Sycoraxic. (TV: The Christmas Invasion) He did not seem to understand French in his second incarnation, (TV: The War Games) but later became fluent in it across several periods of French history. (TV: The Girl in the Fireplace) He also spoke "sabre-toothed tiger" (PROSE: Sick Building), "baby" (TV: A Good Man Goes to War, Closing Time), "cat" (TV: The Lodger) and "horse". (TV: A Town Called Mercy) By his eleventh incarnation, the Doctor purportedly "spoke everything". (TV: A Good Man Goes to War, Closing Time, A Town Called Mercy)

Influence
The Doctor belonged to the Prydonian Chapter, the most important chapter of Time Lord society. (TV: The Deadly Assassin) He had a profound influence on many worlds and was written into their histories (TV: Forest of the Dead); as a result, he was the recipient of many honours including being made a noble of Draconia (TV: Frontier in Space) and a knight (and enemy) of the British Empire. (TV: Tooth and Claw)

Having broken the Time Lords' non-interference policy, in his second incarnation he was put on trial as a renegade. (TV: The War Games) Subsequently, for a time, he acted as agent of the Time Lords' Celestial Intervention Agency before the beginning of his sentence on 20th century Earth. (PROSE: Players, World Game) Following his defeat of Omega, which saved Gallifrey, he was granted a pardon and given his freedom. (TV: The Three Doctors)

In his fourth incarnation, as part of a ploy to outwit invaders of Gallifrey, he was a candidate for the position of Lord President of the High Council. (TV: The Invasion of Time) In his fifth incarnation, he was put on trial again for recklessness. (COMIC: The Stockbridge Horror) He was later given the title of Lord President by Councillor Flavia, against his wishes. He pretended to accept the office but ran away in his TARDIS. (TV: The Five Doctors) Prior to the Doctor's trial during his sixth incarnation, he was deposed in absentia and put on trial for breaking the non-interference policy and later in the same trial, for genocide. The validity of the trial was called into question when it was discovered it had been orchestrated by an evil future manifestation of the Doctor, the Valeyard, and mooted. (TV: The Trial of a Time Lord)

Biographical summary
The Doctor left Gallifrey and became a hero who fought evil and injustice across the universe in violation of the Time Lords' non-interference policy. (TV: The War Games) Technically, he explored only with the intention of experiencing the wonders of the universe and having fun, but frequently became embroiled in machinations and crises that ended with him defeating the foe and saving the planet he was visiting. He travelled with many companions, beginning with his granddaughter, Susan Foreman, who also came from Gallifrey. (TV: "An Unearthly Child", "A Desperate Venture", Gridlock)

Eventually, he was called to account for his crimes against the Time Lords during his second incarnation, when he called them to stop the War Lord and return kidnapped humans to their own era. His punishment was a forced regeneration, exile to Earth in the 20th century, and the loss of his knowledge of how to control the TARDIS. (TV: The War Games) This knowledge was restored to him after he helped to defeat Omega. (TV: The Three Doctors)

Afterwards, he resumed having adventures with many companions in his following incarnations. Early in his Fourth incarnation he was sent by the Time Lords to prevent the creation of the Daleks, but despite having the chance he refrained from committing genocide. (TV: Genesis of the Daleks) After this he kept the Black Guardian from obtaining the Key to Time, (TV: The Armageddon Factor) achieved the office of Lord President of Gallifrey, (TV: The Invasion of Time The Five Doctors) and was again put on trial in his sixth incarnation for breaking the non-interference policy again. He discovered that the Prosecutor, the Valeyard, was a personification of his future evil, who was helping to cover up the crimes of the High Council of Time Lords. (TV: The Trial of a Time Lord)

During the Last Great Time War between the Time Lords and the Daleks, the Eighth Doctor refused to be a part of it. He died in a spaceship crash on Karn, but was revived by the Sisterhood of Karn, and agreed to regenerate into a Warrior. (TV: The Night of the Doctor) The Doctor then fought in the War. (TV: Dalek) He ultimately ended the war, but was able to save Gallifrey with the help of his other twelve incarnations. This displacement of Gallifrey caused the near-extinction of the Daleks. (TV: The Day of the Doctor) Gallifrey and the war were sealed in a time lock, making it impossible to time travel to either. (TV: The Stolen Earth)
 * For details on the Last Great Time War and its survivors, see the separate article.

In an alternate timeline, the Doctor's grave was on Trenzalore, where he had died after a battle. The Doctor was buried in his TARDIS. Instead of a body, the TARDIS contained the Doctor's time stream, manifesting as a column of light. The Great Intelligence forced the Eleventh Doctor to go to Trenzalore to open the TARDIS, though it was opened by a data ghost of River Song. The Great Intelligence entered the timestream to alter the Doctor's history, but the Doctor was saved by Clara Oswald scattering herself through his timestream. Due to this Clara had helped the Doctor many times through his lives, even telling him which TARDIS to steal. (TV: The Name of the Doctor)

The War, Tenth and Eleventh Doctors were brought together by The Moment to try to change the fate of Gallifrey and the Time Lords. Bringing together all of his incarnations together at once, the Doctor succeeded in freezing Gallifrey in a pocket universe but only his eleventh self and twelfth self would remember this. (TV: The Day of the Doctor)

Eventually the time came for the Doctor to go to Trenzalore where he was fated to die in battle. The Doctor spent centuries protecting the town of Christmas from various enemies including the Daleks, Cybermen, Sontarans and the Weeping Angels as the Time Lords were trying to return to the universe through a crack in time there. Growing extremely old and frail, the Doctor came to the end of his life as he no longer possessed the ability to regenerate. At the moment he was to be killed by the Daleks, the Time Lords intervened at the request of his companion Clara Oswald, granting him a new regeneration cycle and allowing him to defeat the Daleks and become the Twelfth Doctor, changing his personal future. (TV: The Time of the Doctor)

The Doctor's incarnations
Through the power of regeneration, the Doctor's personality and outer form changed greatly over time, although all his incarnations were essentially the same person.

The Doctor was known to have regenerated on at least thirteen occasions. (TV: The Time of the Doctor)


 * The First Doctor was an unreadable, guarded figure who was, at first, slow to trust newcomers who learnt of him. This Doctor was often irascible. He made his anger obvious. He was protective of the young women he took on as companions; they reminded him of his granddaughter, Susan. This Doctor was a brilliant, often short-tempered scientist and keen strategist. He used his signet ring to help get himself through ordeals due to his physical age impeding him. He stole a TARDIS and took his granddaughter with him, joyriding through all space and time, without a clue as to how to drive the thing.
 * The Second Doctor, in contrast to his preceding incarnation, was warm and wise. He was as surprised and frightened of alien menaces as those who faced them with him. He had a knack for manipulation and deception. His predecessor would refer to him as a "clown" due to his bumbling nature. He loved tootling on his recorder and carried around a 500-year diary, trying to record his travels, but ended up discarding it. He wore a big fur coat that dwarfed him, tying it closed with twine. A "cosmic hobo," he was forever getting himself in and out of trouble.
 * The Third Doctor was a more dashing figure than his predecessors. He was described by his first incarnation as a "dandy". (TV: The Three Doctors) He had a penchant for inventing gadgets and was skilled at martial arts, particularly Venusian aikido, and owned a vintage car named Bessie. His initially contentious relationship with Brigadier Lethbridge-Stewart softened into a close friendship during his exile on Earth, lasting through his future regenerations, despite not always agreeing with his actions. (TV: Doctor Who and the Silurians) He also displayed great affection for his female companions, particularly Jo Grant. He was a gallant action hero who was very protective of his companions.
 * The Fourth Doctor was more eccentric than his previous incarnations and was the first to seem "young." Rarely without his very long scarf, he always carried jelly babies in his pockets, using them as bluffs, gifts and distractions—and occasionally snacks. He relied on his considerable charm, luck, and experience to get through bad situations. Although he retained his fondness for Earth (TV: The Stones of Blood), he ended his regular association with UNIT almost immediately upon his regeneration and only occasionally returned to the planet. However, he had not properly resigned from the position. (TV: Pyramids of Mars) He hated to work and preferred travelling (TV: Robot) but liked history. He usually travelled with only one companion at a time.
 * The Fifth Doctor was fond of cricket and wore a stick of celery on his lapel. After a difficult regeneration, this Doctor displayed energy, compassion and innocence not seen in his predecessors. His character was very human and vulnerable. Like them, he used improvisation as the best way out of a tricky situation. The Fifth Doctor was the first incarnation since the First Doctor to go "hands free" and forgo the usage of a sonic screwdriver after having it destroyed. He occasionally wore glasses, even though he didn't need them; he only wore them to make himself look clever. (TV: Time Crash) He was the first Doctor to sacrifice himself for another, when he and Peri Brown were dying from Spectrox toxaemia; with only one dose of the antidote available, he gave her the cure rather than taking it himself.
 * The Sixth Doctor was a grandiose and eloquent incarnation. He sported a multi-coloured wardrobe that looked like it was designed by ; it was often commented upon, occasionally leading to him being mistaken for a jester. This Doctor loved a good quote, often making one he deemed appropriate during an adventure. He also proved to have great acting skills on numerous occasions. (TV: Mindwarp, The Ultimate Foe) His manic personality and acerbic wit could shade into moral passion, but his lack of concern for little things disgusted his companions. He was also capable of violent action, much more so than his past lives, even seeing logic in murder. (TV: The Two Doctors) Like the Fourth Doctor, he spent most of his travels with a single companion.
 * The Seventh Doctor had a voice touched by a Scottish burr. A keen strategist and scientist and especially early in his life, lighthearted, this Doctor was a planner of the highest order. Embracing the complexities of time travel and his ability to manipulate and plan for the future, the Seventh fully embraced his role of Time Lord, even if it risked alienating his companions. (TV: The Curse of Fenric) However, he wished to help heal psychological scars which his companions suffered from. (TV: The Greatest Show in the Galaxy, Ghost Light)
 * The Eighth Doctor showed a romantic and sensitive side not displayed by previous Doctors. Less morally flexible than his immediate predecessor, the Eighth Doctor suffered from bouts of amnesia, first after his regeneration and again after Gallifrey was destroyed following the War with the Enemy. (PROSE: The Ancestor Cell) He was broken down after the death of his Great-Grandson Alex Campbell and companion Lucie Miller, who died defeating a Dalek Invasion of Earth. (AUDIO: To the Death) Unlike other Doctors, the Eighth spent his travels crossing between parallel universes (AUDIO: Zagreus, PROSE: Time Zero) and amidst time paradoxes, making his personal timeline hard to piece together. (PROSE: Interference - Book One, Interference - Book Two, AUDIO: Storm Warning)
 * The "War Doctor" was an incarnation specifically chosen to be that of a warrior that would fight in the Last Great Time War. The regeneration into this incarnation was aided by the Sisterhood of Karn. (TV: The Night of the Doctor) His later incarnation stated that his actions broke "the promise" of the "name of the Doctor." (TV: The Name of the Doctor) This assessment changed somewhat once the real end of the Time War was revealed (TV: The Day of the Doctor) and was described after that as being the Doctor most of all by his future selves.
 * The Ninth Doctor considered himself the sole Time Lord survivor of the Time War (he spent his life thinking that he was responsible for decimating the Time Lords). He displayed much of the playfulness of his previous incarnations, but was emotionally and psychologically scarred by the war and his role in it, which sometimes resulted in a detachment that was interpreted by some as cruelty. (TV: The End of the World, Dalek) When asked about his voice and accent, he responded, "Lots of planets have a North". (TV: Rose) He cared deeply for Rose; he began to heal thanks to her. (TV: Dalek) He also made dry jokes when facing danger or to diffuse tension. The Ninth Doctor ultimately sacrificed himself to save Rose's life, not only proving his affection for her, but allowing him to make peace with his past. (The Parting of the Ways)
 * The Tenth Doctor had a manic personality with a fondness for human pop culture references. However, his more outgoing personality traits largely existed to hide leftover emotional trauma from the Time War. While he had a bright, playful side, darker traits occasionally emerged. (TV: The Christmas Invasion, Tooth and Claw, School Reunion, The Runaway Bride) He continued his previous incarnation's love for Rose Tyler, though he was unable or unwilling to express his exact feelings. (TV: Journey's End) He experienced other romances on occasion, including with historic figures Madame de Pompadour (TV: The Girl in the Fireplace) and Queen Elizabeth I. (TV: The End of Time, The Day of the Doctor) However, they all ended badly. He was also the first Doctor to explicitly fear and dodge regeneration, because he had grown attached to his attributes and felt like it was a form of death and loss of identity. When the time came for him to regenerate, he was completely heartbroken before accepting his destiny. (TV: The End of Time)
 * The Eleventh Doctor was smug about his abilities and exhibited a renewed youthful enthusiasm for adventure. He had keen observational skills, and an obsession with seeming trivia. This Doctor could quickly turn frantically angry and ruthless when events demanded. (TV: The Eleventh Hour, The Beast Below, A Town Called Mercy) Like his Second and Seventh selves before him, he was a cunning schemer, executing temporally complex plans and misdirections to achieve victory against his enemies. (TV: Day of the Moon, A Good Man Goes to War, The Wedding of River Song) He frequently referred to himself as being old, showing his age on more than a few occasions. (TV: Vincent and the Doctor, The Big Bang, The Impossible Astronaut, Closing Time) Through his marriage to River Song, he found a sense of family again with her and his in-laws, and was distraught when circumstances separated him from them. (TV: The Power of Three, The Angels Take Manhattan, The Name of the Doctor) In contrast to his predecessor, this incarnation was highly secretive, though for good reason, as several of his greatest secrets would come back to haunt him, ultimately leading to his regeneration. (TV: The Name of the Doctor, The Day of the Doctor, The Time of the Doctor)
 * The Twelfth Doctor, the first of The Doctor's second cycle of regenerations, appeared to help his past incarnations save Gallifrey from being destroyed with the Moment. (TV: The Day of the Doctor)
 * The Valeyard shared the characteristics and dress sense of the Master. The Master explained that the Doctor's darker side became personified during the Time Lord's twelfth through final regeneration. He sought to take the Sixth Doctor's seven remaining regenerations and have them for himself. (TV: The Ultimate Foe) He was finally defeated in Victorian era London. (PROSE: Matrix)
 * The Curator hinted to the Eleventh Doctor that he was a future version of the Doctor. He provided the Eleventh Doctor with clues on what to do next with his life, alluding to the possible survival of Gallifrey and that if he were the Doctor, he would look for it. (TV: The Day of the Doctor)

An interesting aspect of the Doctor's personality was that he occasionally expressed a personal liking for particular incarnations, though this opinion depended on the incarnation making the assessment. The Doctor's tenth incarnation expressed a deep fondness for his fifth incarnation. (TV: Time Crash) The Fifth Doctor was disliked by his immediate successor. (TV: The Twin Dilemma) In another instance, the Fourth Doctor made reference to the Third Doctor, saying, "Some people liked it, but I prefer this one." (TV: The Brain of Morbius) The Seventh Doctor was also annoyed when he had to work with the Fifth Doctor, seeing him as "not even one of the good ones". The Fifth Doctor was equally disgusted by what he would become. (PROSE: Cold Fusion) Immediately before his regeneration, the Tenth Doctor stated, "I don't want to go", showing he had become attached to his current self. Immediately after his tenth regeneration, the Eleventh Doctor remarked upon his new nose, stating that, "I've had worse"—possibly a reference to multiple incarnations, including his third, who was once described as a "long-shanked fellow with a mighty nose". (TV: The End of Time, The Time Warrior) The Eleventh Doctor also at one point expressed loathing for his first incarnation's initial personality, considering himself at that time a foolish and arrogant liar and a selfish coward. (COMIC: Hunters of the Burning Stone) The Eleventh Doctor expressed an even greater hate for the "War Doctor" that he considered a traitor, even stating that he went against "the name of the Doctor" in his actions. (TV: The Name of the Doctor). The Tenth and Eleventh Doctors constantly bickered and joked with each other, upon meeting, similar to a brotherly relationship. In fact, their quirks were so similar that they perfectly mimed each other when stopping Kate Stewart and her Zygon counterpart from bombing London. (TV: The Day of the Doctor)

Regeneration
Due to the unique structure of Time Lord biology the Doctor had the ability to regenerate, to "cheat death". (TV: The Parting of the Ways) A Time Lord was usually limited to twelve regenerations. (TV: The Deadly Assassin, Mawdryn Undead, Doctor Who, The Time of the Doctor) The High Council of the Time Lords could influence regenerations, treating them as punishment (TV: The War Games) and reward. (TV: The Five Doctors, Utopia, The Time of the Doctor) At times, enemies coveted the Doctor's future regenerations and tried to take them for their own. (TV: Mawdryn Undead, Doctor Who, Human Nature/The Family of Blood)

The effect of regeneration on the Doctor in the time immediately following the event varied from incarnation to incarnation. In some cases the Doctor regained his faculties quickly, erratic behaviour notwithstanding. (TV: The Power of the Daleks, The Twin Dilemma, The Eleventh Hour) On one occasion when the regenerative process was postponed for a long time, he was rendered amnesiac. (TV: Doctor Who) In most cases the Doctor was incapacitated for a period of time before ultimately recovering. (TV: Spearhead from Space, Robot, Castrovalva, Time and the Rani, The Christmas Invasion) There was also a unique case where the Doctor (through will or the nature of his injury) was able to delay regeneration from setting in for an extended period of time - long enough to visit all of his past companions - though the resulting energy release was catastrophic for the TARDIS. (TV: The End of Time, Death of the Doctor)

Due to the regeneration into the War Doctor and the Tenth Doctor's aborted regeneration, the Eleventh Doctor was actually the Doctor's last incarnation until the Time Lords gifted him with a new regenerative cycle at the end of that life. (TV: The Time of the Doctor)

Causes of regeneration

 * The First Doctor was weakened by Mondas as it drained Earth's energy, succumbing to old age. (TV: The Tenth Planet)
 * The Second Doctor had regeneration forced upon him by the Time Lords as part of his punishment for breaking the Laws of Time; his appearance was chosen for him after he rejected all choices. (TV: The War Games)
 * The Third Doctor suffered radiation poisoning from the Great One's web of Metebelis crystals, then got lost in the time vortex for a decade before returning to UNIT HQ. (TV: Planet of the Spiders, PROSE: Love and War)
 * The Fourth Doctor was very badly injured after plummeting from the Pharos Project radio telescope. (TV: Logopolis)
 * The Fifth Doctor suffered exposure to unrefined Spectrox, sacrificing himself to give the bat's milk needed to cure it to Peri. (TV: The Caves of Androzani)
 * The Sixth Doctor was weakened from his battle with the Lamprey and began to perish from the sapping of his chronon energy. (PROSE: Spiral Scratch) He escaped in the TARDIS in deep space to take one last look at the universe when the Rani shot down his TARDIS (TV: Time and the Rani) causing him to suffer a "bang to the head", which finished off his failing body. (AUDIO: The Four Doctors)
 * The Seventh Doctor was lightly injured after being caught in the middle of a gang war; his circulatory system was damaged by Grace Holloway during surgery to "fix" his abnormal heart-beat. (TV: Doctor Who)
 * The Eighth Doctor regenerated after he tried to help a pilot named Cass escape from a crashing ship. Cass refused his help however, when she identified his ship as a TARDIS and therefore his being a Time Lord, who she despised because of the Time War. He died when the ship crashed, but was revived temporarily by the Sisterhood of Karn, who not only offered to trigger his regeneration, they also offered him a choice on the characteristics of his next incarnation. (TV: The Night of the Doctor)
 * The "War Doctor" regenerated because his long-lived elderly body had grown precariously weak after an entire lifetime of fighting in the Time War. The tipping point was at the end of the war, when he helped to save Gallifrey from being destroyed by one billion-billion Daleks and place it in a different dimension. With the Time War concluded and his will to persist as that incarnation for as long it waged on settled, his regeneration began before his vitality drained entirely. He remarked that his body was "wearing a bit thin," like his distant predecessor. (TV: The Day of the Doctor)
 * The Ninth Doctor removed the Time Vortex's energy from Rose Tyler, channelling it back into the heart of the TARDIS. However, his brief possession of the energy very nearly destroyed his cellular structure completely. Because of the damage, he had to regenerate. (TV: The Parting of the Ways)
 * The Tenth Doctor was grazed by a shot fired from a Dalek during their 2009 invasion of Earth. He used his regenerative energy to heal himself, but then siphoned off the rest of the cycle into his extra hand to prevent his full transformation into another form. The regeneration energy stored in the hand allowed it to grow into another Doctor, when it came into contact with Donna Noble. (TV: The Stolen Earth/Journey's End)
 * The Tenth Doctor absorbed the radiation from a nuclear vault supply to spare Wilfred Mott from it. Unlike the other Doctors, he held off the regeneration for a long time; the result was explosive damage to the TARDIS that caused it to crash and regenerate itself. (TV: The End of Time)
 * The Eleventh Doctor spent centuries defending the town of Christmas, on the planet Trenzalore. Before his body succumbed to old age, he was granted a new regeneration cycle by the now-surviving Time Lords and began the process when standing on top of the Clock Tower on Trenzalore. This was perhaps his most destructive regeneration process yet, as he destroyed several Daleks and their ship with the regeneration energy. It restored his body to a younger form, but didn't immediately change him into his next incarnation. The change finally occurred shortly after he returned to the TARDIS. (TV: The Time of the Doctor)

Near Regeneration
The Second Doctor nearly regenerated after being shot in the head when confronted by guards on Skybase, causing damage to his skull and frontal lobe. The subsequent fall broke his nose, jaw, right femur, and collarbone, and caused some spine damage. However, an injection of Shiner DNA delayed the regeneration and kept him alive long enough for his body to go into a 6-month healing coma to recover on its own. (PROSE: The Indestructible Man)

The Third Doctor had a near-regeneration experience when he fell off a building during a struggle. He began to regenerate into the Fourth Doctor. Meanwhile, the Nurazh attempted to take over the Doctor's mind, but unable to cope with two Time Lord minds at the same time, it perished, thus healing the Doctor back to his third incarnation. (PROSE: The Touch of the Nurazh)

The Eleventh Doctor was seen seemingly beginning regeneration after being shot by the astronaut, before it was interrupted with another shot, killing him. (TV: The Impossible Astronaut) In truth, it was actually the Teselecta impersonating him and simulating regeneration, with the real, miniaturised Doctor inside. (TV: The Wedding of River Song)

The Eleventh Doctor also nearly died when he was poisoned by River Song. He was then revived by River Song, who used all of her own remaining regenerations in order to save his life. (TV: Let's Kill Hitler) The Doctor later used some of his own regeneration energy in order to heal River's wrist. (TV: The Angels Take Manhattan)

"Doctor Who"

 * For a further in-universe reference of the Doctor's name, please see the "Doctor Who?" running joke.

The use of the name "Doctor Who" when referring to the Doctor is disapproved of by some fans, but is commonplace in the British media, the end credits of many episodes, and most prose and comic stories of the 1960s and 1970s. Indeed, the ending credits for the series gave his name as "Doctor Who" or "Dr. Who", from 1963 until Logopolis part four, when incoming Doctor Peter Davison insisted upon a change in the credits of Castrovalva to "the Doctor". This remained in place through the end of the original series in 1989. Executive Producer Russell T Davies used "Doctor Who" when the series returned in 2005, but Tenth Doctor actor David Tennant asked to change it back to "the Doctor" beginning with The Christmas Invasion.

Throughout the franchise's history it has been common for media and cast members to refer to the character as "Dr. Who". In fact, even Peter Davison and David Tennant have called the character "Doctor Who" in several different interviews.

In the series, only one character, WOTAN in 1966's The War Machines, has ever directly referred to him by this name. In the 2005 episode Rose, a website called "Who is Doctor Who?" is introduced, though the name is presented as a question put forward by a conspiracy theorist and no one actually uses the name in dialogue. A line of dialogue written for TV: The Empty Child, but cut, would have had the Doctor himself use the name as part of a joke involving  (after being hailed as by Rose, the Doctor was to have muttered, "I'd rather be  than Star Trek").

Other media, 1960s and early 1970s Doctor Who annuals, comics and Target Books (most notably the Doctor Who and the Zarbi, not technically a Target Books novelisation, but reprinted by them) have called the Doctor "Doctor Who". Even then, dialogue between characters usually referred to him as "the Doctor".

Casting
, every actor to portray the Doctor has been male, white, and born in the United Kingdom. Despite the fact that the Doctor is not a native of Britain, or of Earth for that matter, every actor to play him so far has had a British accent, much in the way most aliens in the Star Trek franchise tend to speak with an American accent. The type of British accent has varied from one incarnation to the next. The earliest incarnations used RP, whereas more recent incarnations have had Estuary accents. The Ninth Doctor was unique in that he had a Northern accent, causing Rose to ask why an alien would have a Northern accent, to which he replied, "Lots of planets have a north." (TV: Rose) To date the oldest actor to be cast as the Doctor has been John Hurt, who was 73; the youngest has been Matt Smith, who was 26 when cast. In 2012, Tom Baker was 78 after his appearance in Big Finish Productions' Fourth Doctor Adventures audio dramas was released, making him the oldest actor to play the part in an officially licensed capacity. Peter Davison, Colin Baker, Sylvester McCoy and Paul McGann, all in their fifties, sixties or seventies, also continue to portray the Doctor in licensed audio dramas produced by Big Finish, with McGann also appearing in audio dramas produced by Big Finish and BBC Radio for broadcast on BBC7 radio. In the 2000s and 2010s, Tom Baker also portrayed the Doctor in AudioGO's Hornets' Nest, Demon Quest and Serpent Crest audio dramas.

Although the character is portrayed as white, there have been black actors who were considered for the role. Among them included comedian Eddie Murphy back in 1996, David Harewood, Charles Venn, Paterson Joseph and Robbie Gee. Colin Salmon was a strong contender to play the Eleventh Doctor.

Longest-serving Doctor
There are several different methods for calculating who was the "longest serving Doctor". The most commonsensical definition is simply that of the actor who played the role on television for the longest continuous period. This mantle goes to Tom Baker, who was the Fourth Doctor from June 1974 to March 1981, or 6 years, 9 months. Baker is also the longest-serving Doctor in terms of number of individual episodes, total story count and amount of screen time. Thus he is generally considered to be the "longest-serving Doctor".

But there are other methods of measurement — all of which exclude Dimensions in Time.
 * Matt Smith's Doctor is the longest-lived Doctor on screen, spending at least 1200 years of his life in this incarnation (300 during his regular run and 900 during his exile on Trenzalore).
 * For 92 of the 104 Saturdays that comprised 1964 and 1965, William Hartnell's credit appeared after each episode of Doctor Who without fail. Sure, he did sometimes take a holiday and pre-film the odd insert, but, to paraphrase WOTAN, "Dr. Who was required" for all but six weeks in both 1964 and 1965. Call Hartnell the "longest-serving-within-a-single-year-Doctor".  Troughton is the closest Doctor to this record, but by 1966, Doctor Who was getting more like an eight- or nine-week gap each year.
 * Peter Davison holds the record for the greatest length of time between his initial performance in the last episode of Logopolis, and Time Crash . The two events were separated by 26 years 8 months.
 * Paul McGann had the longest run between bookending regeneration scenes. The span from the premiere of Doctor Who to his regeneration in The Night of The Doctor was approximately 17 years and 6 months.
 * Paul McGann was notionally the longest-serving incumbent in the role, as he debuted in May 1996 and Christopher Eccleston's premiere didn't happen until March 2005. Being very generous, therefore, McGann was the "current Doctor" for a total of 8 years and 10 months.  However, this is probably stretching a point, since obviously he was actually replaced not once but twice by the BBC.  He effectively lost his incumbency once Richard E. Grant was cast as the Shalka Doctor.
 * McGann is on more solid ground when all forms of media are considered., he's starred in more performed Doctor Who, given his prolific run on audio, than anyone else.  If audio is considered as an equal performed art to television, he has far surpassed even Tom Baker in terms of amount of recorded material featuring his Doctor — though the fact that Baker began recording audio adventures  threatens McGann's record.
 * The Eighth Doctor, though not McGann himself, is the longest-serving incumbent comic strip Doctor, in terms of the amount of time between his debut in Dreadnought on 1 June 1996, and his final appearance in The Flood on 2 March 2005. Call it 8 years and 9 months.
 * The Tenth Doctor is the longest-serving comic strip Doctor, in terms of the total number of stories which featured his incarnation. This is primarily due to the number of different publications that were granted comic licences during David Tennant's tenure in the role.
 * The situation with books is a very close battle between the Seventh and Eighth Doctors, both of whom had long-running series. However, the Eighth Doctor is the longest-running both in terms of time and number of books published, as seen at this list of novels per Doctor.

The issue of the longest-serving Doctor was a source of controversy on British game show, which asked the question with the choices of McCoy, McGann, Eccleston, and Tennant; the team split their £650,000 between McCoy and McGann, only to find out that the "correct" answer was Tennant. Once the error was discovered (partly since the question was fundamentally flawed due to the absence of Tom Baker), the team was brought back to continue where they left off with £325,000 and ended up winning £25,000.

Analogous characters
There have been several characters outside the confines of the DWU which have been broadly modelled on general aspects of the Doctor. Such "pastiches" are examined in greater detail elsewhere.

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