The Doctor

"Some fifty years ago, I knew a man who solved the insoluble by the strangest means. He sees the threads that join the universe together and mends them when they break."

- Zastor, "Meglos"

The Doctor (also known by a number of other aliases) is a somewhat eccentric and renegade alien of unknown origins, who was found beneath an interdimentional portal as a child. For most of his/her life, he/she was believed to be a Time Lord - a humanoid alien from the planet Gallifrey - although this was later revealed to be false.

The Doctor is a time traveler of great intelligence who battles injustice throughout our universe (and sometimes in others as well) while exploring both time and space in a stolen TARDIS - Time and Relative Dimension in Space - a living time machine, dimensionally transcendental, making it much bigger on the inside than the outside. Few people know his actual name apart from himself; companion Samantha Jones; one of his wives, River Song; and possibly Petronella Osgood, as he once told her that his first name was Basil. Whether that's true or not remains unconfirmed.

His favorite planet is Earth, a world he has visited countless times and even lived on for years on multiple occasions, both willingly and while in exile. Due to a malfunction in the chameleon circuit that has never been properly fixed, his TARDIS assumes the shape of a 1950s-style British police box.

Like all Time Lords, the Doctor has the ability to regenerate his body to avoid death, assuming a new appearance and even modifying some aspects of his personality, although his memories and basic identity remain the same. His alien nature also gives him a form of time sensitivity, allowing him deep and instinctive understanding of time, the ability to discern moments which are "fixed" from those which can be altered without harming the space-time continuum, as well as the ability to sense when there is something wrong with the timeline.

In his First incarnation, the Doctor expressed a very strong aversion to altering history in any way during his travels. This conviction has faded more and more as his hatred of injustice overcame his wish to avoid interfering with other civilizations. During all of his travels, the Doctor opposes violence, forceful conquest, slavery and genocide; always siding with the explored victims to overcome their tyrannical invaders and/or masters.

The Doctor's personality is a complex one, and as stated above, tends to fluctuate between his multiple incarnations. He is known to be friendly and humorous, although often a little vain and even arrogant; and may alternate from childishly cheerful to deadly serious depending on the situation. He will seldom lose patience, though, and often manages to remain in control of the situation by manipulating others subtly or pretending to be much less intelligent and resourceful than he actually is. He rarely shows respect for authority but has a deep sense of respect towards all life and never tolerates injustice or prejudice. He tends to dress in an extravagant manner, carries a load of useful and useless items in his pockets (which like his TARDIS are known to be bigger on the inside), remarks casually about the most fantastic subjects and rarely feels the need to explain himself. He is, however, on most occasions, very kind and gentle towards his companions and even complete strangers. He is very compassionate, and will defend even villains from harm, although there have been exceptions. When he absolutely needs to, he is not by any means incapable of killing.

Having lived for hundreds of years and visited hundreds of worlds and epochs, the Doctor remains an intensely curious and highly moral adventurer who will rather solve problems with his wits than by using violence, even though many of the beings he encounters tend to be hostile, especially towards him. The Doctor has a special affection for the Human race and our history and is nearly always accompanied by a Human companion, often female, although neither being exclusive. He is a pacifist by principle and therefore never carries a weapon and has the uncanny ability to keep his enemies distracted just long enough to have worked out a clever way to defeat them. Still, as stated above, he has executed criminals on certain occasions, especially in his Sixth incarnation and his post-Time War incarnations.

Family
The Doctor was allegedly born on the planet Gallifrey in the constellation of Kasterborous. Although little is known of his early life, he seems to have been raised in a conventional family, once fondly recalling the time he watched a meteor shower at the top of a grassy hill with his father.

The Eighth Doctor was infamously revealed to be half-Human on his mother side, but this is usually regarded as having been purposely falsified by him to fool the Master. In the novel Lungbarrow, it is stated that Time Lords practice artificial reproduction and the youngsters - which are born already as adults physically - are raised in families of 45 or so members which refer to each others as "cousins". This is heavily contradicted by a number of canonical and expanded universe sources, though. The same novel also reveals the Doctor to be the literal reincarnation of a historical Gallifreyan figure known as the Other.

No members of the Doctor's family have been seen in canon other than his granddaughter Susan, who traveled with him during his first incarnation and was left to start her own life on Earth circa 2150, following the Dalek invasion of the planet. The Doctor has sometimes mentioned members of his family, such as his father as stated above, as well as an uncle fondly remembered by the Seventh Doctor. It was revealed that he had a brother in the form of Irving Braxiatel, who works for the Gallifreyan Council. He seems to have lost all contact with his family after he left the planet, though whether this is intentional on his part remains unclear. Once asked if he had a family, the Seventh Doctor responded that he didn't know.

Many centuries after Susan's departure, the Eighth Doctor adopted an orphaned Gallifreyan girl and raised her on Earth as Miranda Dawkins. She would later have a daughter, Zezanne, who is implied to have lost her memory and assumed the identity of Susan, meaning that Susan may have never been the Doctor's biological granddaughter to begin with. However, there have also been hints that Miranda's biological father was none other than a future version of the Doctor himself.

Susan herself would later settle down on 22nd century Earth, marry a Human named David Campbell and have a son, Alex Campbell. The Tenth Doctor also had a "daughter" called Jenny, created from his genetic material on the planet Messaline. She was shot and the Doctor believed her to be dead, but was later revived and fled the planet in a ship seeking to explore the universe just like her father.

Old comic books featured the First and Second incarnations of the Doctor travelling with his grandchildren: two kids named John and Gillian. These stories were acknowledged as taking place in the Land of Fiction in the novel Conundrum, whilst an Eighth Doctor comic shows them as dreams of the Doctor. Canonically, they likely never existed, but might be considered part of an alternative universe similar to that of the Peter Cushing movies.

In the matters of love the Doctor has often shown to be mostly uninvolved. The First Doctor was briefly engaged with an Aztec woman called Cameca, and the Fourth Doctor seems to have some romantic affection for Romana, a fellow Gallifreyan who traveled with him extensively. All the other incarnations have been thoroughly asexual until the Seventh. From the Eighth onward all incarnations of the Doctor have had some form of crush, and the Eleventh one eventually got married to an archaeologist and fellow time traveler named River Song. The Tenth Doctor got married to Queen Elizabeth I in the 16th century, although this was somewhat by accident, as he believed she was a Zygon in disguise at that point and proposed to her as a means to attempt to unmask her.

Life on Gallifrey
The Doctor studied in the Prydonian Academy of Gallifrey under the guise of teachers such as Borusa (who would later become President of the High Council) and Azmael, whom he remained friends with until his Fourth incarnation at least. Before leaving Gallifrey, the young Doctor was also a pupil of K'anpo Rimpoche, a wise hermit who lived on the side of the mountain behind his house, and told stories to the young Gallifreyans atop of Mount Cadon. While studying at the Academy, the Doctor was a member of a student society known as the Deca, along with several friends who would later become his enemies, or at least fellow renegades, including the Master, the Rani, the Monk, the War Chief and Drax. The latter would meet the Doctor again in his Fourth incarnation, reminiscing about the "tech course" they attended together.

Name and Aliases
The Doctor's real name has never been revealed, though he has been known by many names and aliases across the universe. His friends at the Academy knew him by the nickname Theta Sigma (ΘΣ), or simply Thete. To his companion Ace, the Seventh Doctor was always "the Professor". The Daleks of Skaro, whose plans for galactic conquest have been repeatedly foiled by the Doctor, came to know him as "the Oncoming Storm". The same title is used by the Draconians (Karshtakavaar in their language), although they are usually allies of the Doctor. The Chelonians meanwhile know him by the much less flattering title of Sla-Ifrok-Yalkoz-Slan, meaning "Interfering Idiot". To the Galyari, he's also known as "the Sandman".

Whenever he needs a name on Earth he usually chooses the alias of "John Smith" or "Dr. John Smith", or a variation of it such as "Johann Schmidt" while on Germany and "Jean Forgeron" while on France. In the parallel universe where the Arthurian legends happened, the Doctor is known by the name Merlin, although it isn't clear whether this Doctor is native to that universe or is a future version of the normal space Doctor who traveled to the parallel reality.

Despite all these alternate aliases, the Doctor identifies strongly with the name he chose to be called, referring to his choice of being known as "the Doctor" as being like a promise he made. Both the First and Tenth Doctor have been known to get annoyed when the title is shortened to "Doc".

It should be noted that the name "Dr. Who" was never directly used by the Doctor onscreen (save for the Peter Cushing movies, which are considered non-canonical), but was used extensively in production material, episode credits and even some episode titles in the sixties and seventies. He was once explicitly and inexplicably referred to as "Dr. Who" onscreen by the intelligent computer system WOTAN; once presented himself as "Dr. von Wer" ("Dr. of Who" in Germany); and the car plate of his beloved vehicle Bessie reads WHO 1.

The Doctor has sometimes claimed that his real name would be unpronounceable to Humans, but whether this is true or not, it is clear that the alias is treated as an official name even on Gallifrey, as the Time Lords have referred to him exclusively as "the Doctor" during his trials. There is evidence that the Doctor may have reasons to hide his real identity, as there have been multiple instances of telepaths probing his mind and finding that his name was "hidden" and inaccessible. Despite that, there are at least two companions – Samantha Jones and River Song – to which the Doctor apparently revealed his name. He also came close to revealing it to Peri Brown once, but she interrupted him.

The Twelfth Doctor once told Osgood that his first name was Basil, to which she responded that hers was Petronella.

Significance of the Word "Doctor"
There is evidence that the meaning of the word "doctor" is the result of a time loop: as it was the Doctor's beneficial interference with past civilizations that resulted in the current meaning of the word to refer to a wise man or healer. In some places, however, the word has acquired different meanings, for instance: in the cultures of the Gamma Forests, the word "doctor" has come to mean "mighty warrior".

The Doctor does have scientific qualifications that would justify his title: he has been shown to be highly skilled in physics, chemistry, engineering, linguistics and other sciences, as well as having a distinguished knowledge of galactic history and law. He graduated from the Prydonian Academy, class of 92, but exactly what he studied there is not clear. One area in which the Doctor's credentials are particularly controversial is medicine, as despite often proving himself quite capable of treating diseases and diagnosing conditions, he has repeatedly denied being a medical doctor. However, the Second Doctor once claimed that he did get a degree in medicine under Joseph Lister in Glasgow, 1888. The Seventh Doctor would later claim that he has a medical degree from Edinburgh, 1870; and the Tenth Doctor later revealed that his teacher at Edinburgh was no other than Joseph Bell. The Fourth Doctor also holds an honorary degree from St. Cedds, Cambridge, 1960. And the Eleventh Doctor also claimed to have a PhD in cheese making.

Question Marks
The Doctor seems to enjoy having an aura of mystery around him, and has been known to sign documents with a question mark on at least two occasions. The question mark symbol is present in his usual attire from the Fourth through the Seventh incarnations. The Third Doctor had a serpent shaped like a question mark tattooed on his arm, although the fact that it is seen as soon as he is awakened from regeneration implies that he didn't tattoo it himself, but had it placed on him by the Time Lords responsible for this forced regeneration for one reason or another. Either that or the tattoo belonged to the Second Doctor and was retained in this regeneration process but lost in the next ones (it is no longer present in the Eighth Doctor).

Life and Travels
Like so many other things about him, the Doctor's age is also a bit of a mystery. He once claimed to be 450 Earth years old in his Second form, and would consistently refer to his age being around 750 in his Fourth form. But since his Sixth form onward he has continuously claimed to be around 900 or 950, never increasing the number despite the many decades and even centuries likely spent on each incarnation. Only in his Eleventh form would he finally admit to being over a thousand years old.

At some point in his life (later dialogue suggests this was when he was 236 years old), the First Doctor left Gallifrey with his granddaughter Susan, stealing an old type-40 TARDIS to travel through the universe, anywhere in space and time. It has been revealed that the acronym TARDIS was invented by Susan, but it seems to have caught on since other Time Lords consistently use the word as well to refer to their own vessels.

After many voyages, the Doctor and Susan settled down to live in London in the 1960s (chosen for being Susan's favorite period of Earth history) where she studied in Coal Hill School. As it happened, her extremely sophisticated knowledge in scientific areas and suspiciously limited knowledge of common subjects led two of her teachers to become curious and investigate about her. They found that she seemed to live in an old police box in a junkyard and ended up meeting the Doctor and discovering about the TARDIS, after which the Doctor refused to let them out, fearing that they would reveal his alien nature to the world. He activated the machine, leading them to prehistoric Earth. Due to the TARDIS' faulty navigational system at the time, the Doctor was never properly able to return the teachers, Ian and Barbara, to their own time, but lived numerous adventures with them over time and space, forging an increasingly strong friendship that would later lead to his increasing admiration for the Human species and the trend of most of his companions being 20th century Earthlings. It was also during these travels that he eventually decided that it was time for Susan to depart and start her own life, which she did on Earth following the Daleks' invasions of 2150. Ian and Barbara would later make it back to the 1960s using a Dalek time machine.

The Doctor's reasons for leaving Gallifrey were never fully detailed, although it has to do with his annoyance over the Time Lords' strict non-interference law, in which they would simply observe the galaxy and never use their mighty power in anyone's favor, not even to save defenseless civilizations from evil conquerors and other atrocities. When he first met Ian and Barbara the First Doctor referred to him and Susan as "exiles; cut off from [their] own planet, without friends of protection" and tells that one day they would come back. Many adventures later, after losing a number of companions and believing that Steven has abandoned him as well, he talked to himself wondering if perhaps he should go back to his world, but claims that he can't.

It appears that during his First and Second lives the Doctor was viewed by fellow Gallifreyans as a fugitive for his crimes of continuous interfering and for stealing the TARDIS. The Second Doctor was eventually caught as he felt himself obliged to contact the Time Lords to have them deal with the War Chief and return the War Lords' abducted victims to their respective periods and places. The Time Lords put him in a trial and found him guilty, sentencing him to exile on Earth during the 1970s and a forced regeneration, resulting in the Third Doctor. During that time, the Doctor served as an unofficial scientific adviser to UNIT, an international Earth military agency created to deal with extraterrestrial threats and other hazards.

After he defeated Omega and saved Gallifrey as well as the rest of the universe, his exile was finally lifted, with the Time Lords allowing him to travel in his TARDIS again. After that, the Third and Fourth Doctors were often sent on specific missions by the Time Lords (as it turned out, even the Second Doctor has been involved in such missions in the period between his trial and the execution of the sentence). Much later on, the Sixth Doctor would also face trial from the Time Lords for his reckless behavior, though this was ultimately revealed to have been plotted by the Master along with the Doctor's own evil side, personified in the form of the Valleyard at some point between his Twelfth and final forms.

Despite rebelling against the Time Lords' due to their attitude in regards to non-interference, the Doctor himself in his First incarnation was extremely rigid about not wanting to rewrite Earth history, such as to prevent the fall of the Aztec civilization or St. Bartholomew's Day Massacre. In retrospect, it is likely that he either thought these to be fixed points in time or was otherwise attempting to prevent paradoxes since he was traveling with earthlings, whose actions in the past might have had consequences for themselves in the future. In any case, he became far more relaxed in this subject in later incarnations, only refusing to save people when dealing with a fixed point in time which could not be altered without putting the universe at risk.

The Doctor's many centuries worth of traveling have led him to become a prominent, if largely unknown figure in Earth history. He has been close friends with Leonardo Da Vinci, William Shakespeare and Winston Churchill; was responsible for the Great Fire of London and the eruption of Mr. Vesuvius which destroyed Pompeii; and was instrumental in preventing and fighting off alien invasions, especially during his time as UNIT's scientific adviser in the 20th century. On multiple occasions he attempted to negotiate peace between the Humans and waking colonies of Earth's previous denizens the Silurians and Sea Devils, but was never successful.

He is acquainted with countless historical figures and friends with many. The famous writer Mary Shelley has been one of the Eighth Doctor's traveling companions. The Fourth Doctor's scarf was knitted to him by Madame Nostradamus, and the Tenth Doctor's coat was said to have been given to him by Janis Joplin. The Doctor once hid himself on a tree and purposefully hit a young Sir Isaac Newton with an apple, prompting him to ponder about the law of gravity. The Doctor also seems to be a friend of Einstein, having once saved him from one of the Rani's plans and once borrowed his toothbrush. The Eleventh Doctor also possesses what he claims to be a picture of himself along with Einstein and Santa Claus, "or as I've always known him, Jeff". The first three incarnations have indeed met Santa Claus (the First in a comic; the Second and Third in short stories). The Seventh Doctor also met Sherlock Holmes and Dr. Watson, although he claims these aren't their real names. This is somewhat contradicted by the Fourth Doctor having met their creator or supposed creator, Sir Arthur Conan Doyle.

The Doctor would also continue to help UNIT and his friend Brigadier Lethbridge-Stewart in subsequent incarnations, up until his Eighth at least. By the early 21st century and possibly earlier his existence was the subject of conspiracy theories. By the 22nd century, the Doctor and UNIT have become a far better known part of Human culture, with the existence of an opera based on the events of Battlefield. He has also became famous (and sometimes infamous) in numerous other worlds, being admired and recognized as a savior in Draconia, Karfel and Tigella, among others.

By the time of his Eleventh incarnation, the Doctor had become such an influential figure in the history of the universe that, when the Great Intelligence attempted to eliminate him in the past, dozens of star systems started to vanish from the skies immediately, in a testimony of how many civilizations own their survival to his past actions.

Although the circumstances of his death have not been revealed, the Doctor once visited his own grave on the planet Trenzalore: it is revealed that his tomb is the wrecked TARDIS, which has grown gigantic due to deterioration of the dimensionally transcendental structure.

Last Great Time War
When the Doctor was in his Eighth incarnation a huge temporal war erupted between Gallifrey and Skaro. At first trying to remain his pacifist self, the Doctor eventually realized that the war was having such a devastating impact on the universe, and his own race had became so corrupt, that to the common people there was no longer any difference between Time Lords and Daleks. When fatally injured in a crash, the Doctor was offered by the Sisterhood of Karn the chance to regenerate into any form he needed to. Despite going against all his principles, he decided to become what the universe needed at the moment: a warrior. This new incarnation, known as the "War Doctor", ultimately caused the annihilation of both species in war, causing the Doctor to become the last of his kind. The Eleventh Doctor apparently regrets what he had became during that period, as he refuses to acknowledge the War Doctor as deserving of being called "the Doctor", claiming he betrayed everything that name stood for.

However, it was later revealed that the War Doctor didn't destroy Gallifrey, but worked together with his Tenth and Eleventh incarnations to develop a way to hide the entire planet in a pocket universe, frozen in time like a painting. At the peak of the war, as the entire Dalek fleet encircled Gallifrey and prepared to fire, all thirteen incarnations of the Doctor arrived with their TARDISes, coordinating an effort to hide the planet, causing the Daleks to destroy each other. All but the Eleventh forgot about this effort to save the planet upon returning to their own times, resulting that the Ninth and Tenth Doctors (and the Eleventh as well up to that point) had to live their lives believing themselves to have destroyed their homeworld. As the Eleventh Doctor found out, the effort had indeed been successful, meaning that Gallifrey and all its inhabitants are preserved somewhere, frozen in time, waiting to be found.

The First Doctor
Played by William Hartnell, 1963-66

By the time he left his home planet, the First Doctor had the appearance of an old white haired gentleman, and usually dressed in Edwardian clothes. He is notably gruffer than most of the later Doctors, although also having a playful side. He tends to stress the importance of not allowing history to be altered.

Above everything else, this Doctor is a scientist, and a very enthusiastic one, who puts his intense curiosity above almost everything, although often worrying about safety as well. He tends to have a paternal attitude towards not only his granddaughter but later Human companions as well. This is the Doctor who first met the Daleks and the Cybermen, among others. Besides the implication of marriage or at least a romantic involvement in the past, since he is a grandfather, this Doctor is one of the only ones to be shown having a romantic affection onscreen, as he briefly becomes engaged to an Aztec woman called Cameca.

Also one of the only Doctors to wear reading glasses, along with the Fifth, the Tenth, the Eleventh and Peter Cushing's "Dr. Who". Most importantly, he is the only Doctor to wear the signet ring, a device with numerous utilities, including exerting control over the TARDIS, facilitating hypnotism and protecting him from electrical shocks. Another unique aspect to this Doctor is his physical fragility due to advanced age, as he is shown to be far less resilient to radiation and temperature extremes, and more easily tired by physical activity than later forms. He eventually became one of three Doctors known to have regenerated due to old age (the other being the War Doctor and the Eleventh Doctor), as he collapsed in his TARDIS while on Mondas and was transformed into the Second Doctor.

Companions:
 * Susan Foreman – The Doctor's granddaughter from Gallifrey.
 * Barbara Wright – A history teacher from 1960s London.
 * Ian Chesterton – A science teacher from 1960s London.
 * Vicki Pallister – A young woman from the 25th century, who the Doctor met as a survivor on Dido.
 * Steven Taylor – A starship pilot from the future, who the Doctor met as a prisoner on Mechanus.
 * Katarina – A young servant from 12th century BC Troy.
 * Sara Kingdom – A Space Security Service agent from the late 40th century.
 * Oliver Harper – A city trader from 1960s London.
 * Gillian – The Doctor's granddaughter, who may or may not have existed.
 * John – The Doctor's grandson, who may or may not have existed.
 * Dodo Chaplet – A young woman from 1960s London.
 * Polly Wright – Also a young woman from 1960s London.
 * Ben Jackson – A young sailor from 1960s London.

The Second Doctor
Played by Patrick Troughton, 1966-69

The Second Doctor is a diminutive man with the appearance of being around his 40s, wearing old clothes, baggy pants and a large black fur coat as well as a bow tie. Shortly after regenerating he immediately discarded the signet ring and would later start using an even more versatile tool in the form of the sonic screwdriver. This Doctor cultivated a warm, playful and informal attitude but would often fool his enemies by proving himself far more resourceful than he seems. He fought the Great Intelligence and participated in the events that lead to the creation of UNIT. He was eventually put on trial by the Time Lords and started to work for them on selected missions before being sent to Earth on exile and forced into regeneration.

Companions:
 * Polly Wright
 * Ben Jackson
 * Jamie McCrimmon – A Highlander Scottish warrior from the 18th century who viewed the Doctor as something of a mystique or magician.
 * Victoria Waterfield – A teenage woman from the late 19th century, made orphan by the Daleks.
 * Zoe Herriot – A young scientist from the late 21st century.
 * Gillian
 * John

The Third Doctor
Played by Jon Pertwee, 1970-74

A tall and dandy figure clad in an elegant outfit with frilled shirt and caped coat. His appearance is of that of a man in his late 50s. He worked for many years as UNIT's unofficial scientific adviser and was the one who made first contact with the Silurians after their long period of hibernation. He is extremely skilled with technological equipment and also much more of an action man than his two predecessors, as he is quick to engage in hand to hand combat as well as sword fight, and knows how to pilot a number of vehicles; from his yellow roadster Bessie to a curious hovercraft-like machine known (not onscreen) as the Whomobile. He most famously practices the martial arts style known as Venusian Aikido. Despite all this, he is also one of the most gentle, caring and compassionate of the Doctors, and proudly stands for peace whenever the situation. He formed a lasting friendship with Brigadier Lethbridge-Stewart and Jo Grant. Regenerated after being exposed to excessive levels of radiation while defeating the Old One, leader of the Eight Legs of Metabilis III; his regeneration was assisted by his old guru K'anpo Rimpoche.

Companions:
 * Brigadier Alistair Gordon Lethbridge-Stewart – Key founder and commander of the UK branch of UNIT.
 * Liz Shaw – A 20th century UK UNIT civilian scientist.
 * John Benton – A 20th century UK UNIT sergeant.
 * Jo Grant – A 20th century UK UNIT member assigned as an assistant to the Doctor.
 * Mike Yates – A 20th century UK UNIT captain.
 * Sarah Jane Smith – A 20th century investigative journalist.

The Fourth Doctor
Played by Tom Baker, 1974-81

The Fourth Doctor has a very iconic appearance, as a tall and lanky man with wild brown hair and wearing distinct attire including his overly long scarf. His behavior is notably playful and childlike during most of time, and his fondness for Jelly Babies (already present in the Second Doctor) is legendary. But like the Second, his appearance and behavior tend to conceal a very clever and resourceful mind. He typically adventured on his own or accompanied by a single companion, and would also occasionally still get involved with UNIT or get sent on specific missions by the Time Lords. He was also contacted by the god-like being known as the White Guardian and sent to find the shattered remains of the key of time and prevent it from falling into the hands of the Black Guardian. He regenerated on the planet Logopolis and was assisted in regeneration by a mysterious avatar of himself known as the Watcher.

Companions:
 * Sarah Jane Smith
 * Harry Sullivan – A 20th century UK UNIT surgeon lieutenant.
 * Leela – A warrior woman from the Sevateem tribe, native to an unnamed planet.
 * K-9 MK I – An intelligent robotic dog originally owned by Professor Marius on the asteroid K4067.
 * Ann Kelso – A police officer from 1970s England.
 * Mrs. Wibbsey – The Doctor's housekeeper in Nest Cottage, originally from the 1930s.
 * Mike Yates
 * K-9 MK II – A replacement model developed by the Doctor after MK I's departure.
 * Romana – A young Time Lady from Gallifrey assigned to help the Doctor obtain the Key of Time.
 * Sharon Davies – A young student from 1970s Blackcastle.
 * Adric – A young man from the planet Alzarius who stowed away in the TARDIS.
 * K9 MK III – A replacement model developed by the Doctor and eventually sent to Sarah Jane Smith.
 * Nyssa – A Princess of the planet Traken.
 * Tegan Jovanka – An stewardess from 1980s Australia, who the Doctor met in London.

The Fifth Doctor
Played by Peter Davison, 1981-84

The Fifth Doctor had a much younger appearance than his predecessors and dressed in an old fashioned cricket uniform with a stick of celery on his coat which he claimed would turn purple in the presence of certain substances in the air to which he was allergic. He tended to be one of the most idealistic Doctors. Contrasting with his immediate predecessor, he enjoyed traveling with two or more companions, although he also spent numerous years traveling just with Nyssa. He is very enthusiastic about the game of cricket, and is a skilled player. After being separated from his TARDIS and stranded on the ice planet Pella Satyrnis, the Fifth Doctor was adopted by a Hroth family and spent five years living in the planet, administering a restaurant. At a later point in life he lived in a house in 107 Baker Street from 1867 to 1868 along with his assistant Robert McIntosh, during which he grew a beard and became known as a respected scientific authority using the name Dr. Walters. He regenerated on the planet Androzani Minor after sacrificing himself to save his companion Peri.

Companions:
 * Adric
 * Nyssa
 * Tegan Jovanka
 * Gus Goodman – A fighter pilot from an alternate timeline where WWII was ongoing in the 1960s.
 * Thomas Brewster – A young orphan from mid 19th century London.
 * Hannah Bartholomew – A huntress from 1910s England.
 * Vislor Turlough – A young man from the planet Trion, who the Doctor met in 1980s England.
 * Kamelion – A sophisticated shape-shifting robot who was previously controlled by the Master.
 * Peri Brown – A young botanist from 1980s Baltimore, who the Doctor met in Lanzarote.
 * Erimem – A would-be Pharaoh from the ancient 14th century BC Egypt.
 * Amy (aka Abby) – A tracer assigned by the Grace to help the Doctor obtain the Key to Time (again).

The Sixth Doctor
Played by Colin Baker, 1984-87

The Sixth Doctor is the most flamboyant incarnation, with a brash, overbearing personality and dressed in bright, mismatched clothes. His egotistical behavior hides that he still retains a sense or morality and empathy. Encountering old foes like the Master, Daleks, and Cybermen, he even meets the Valeyard, a evil future incarnation of the Doctor himself. He regenerates after an attack by the Rani.

Companions:
 * Peri Brown
 * Frobisher – A shape-shifting Whifferdill from 82nd century Xenon.
 * Grant Markham – A computer programmer from 22nd century New Earth.
 * Evelyn Smythe – A professor of history from 2000s England.
 * Thomas Brewster
 * Jason – A young aristocrat from 18th century France.
 * Crystal – A young nightclub singer from 1980s England.
 * Zog – An Aldeberian from Deneb IV, who the Doctor met as a slave on Sentros.
 * Charlotte Pollard
 * Mila – A young woman who sneaked aboard the TARDIS during a chase by the Daleks.
 * "Jamie McCrimmon" – An older version Jamie created in the Land of Fiction.
 * Henry Gordon Jago – An impresario and amateur investigator from late 19th century England.
 * George Litefoot – A pathologist and amateur investigator from late 19th century England.
 * Flip Jackson – A young woman from 2010s London.
 * Constance Clarke – A WREN from 1940s England.
 * Melanie Bush – A computer programmer from 1980s Pease Pottage.

The Seventh Doctor
Played by Sylvester McCoy, 1987-1996

The Seventh Doctor starts off whimsical, but becomes manipulative by the end of this incarnation. Dressed in a tan colored jacket, panama hat, and a sweater vest adorned in red question marks, he thwarts the Rani in the beginning of his time and takes in Ace, a human transported from the 1980's into the future, and teaches her about the universe. After being wounded in a gang shoot-out in 1999 San Francisco, he dies after the surgeons working on him got confused over the Doctor's two hearts and lodges a cardiac probe in him.

Companions:
 * Melanie Bush
 * Ace McShane – A young woman from 1980s Perivale, who the Doctor met on Svartos in 2 billion.
 * Frobisher
 * Raine Creevy – A young safecracker from 1980s England, who was born under the Doctor's aid.
 * Bernice Summerfield – An archaeologist from the 26th century, who the Doctor met on Heaven.
 * Chris Cwej – An adjudicator from 30th century Earth.
 * Roz Forrester – An adjudicator from 30th century Earth.
 * Hex Schofield – A young nurse from 2020s England.
 * Sally Morgan – A young soldier from 2020s England.
 * Lysandra Aristedes – A former Forge soldier from 2020s England.
 * Antimony – An android created by the Doctor.
 * Elizabeth Klein – A scientist from an alternate 1980s England, in which the Nazis won WWII.
 * Will Arrowsmith – A UNIT junior science officer from 1990s England.
 * Catherine Broom – An android created by the Doctor.

The Eighth Doctor
Played by Paul McGann, 1996, 2013

The Eighth Doctor was effortlessly romantic and charming, and was the first incarnation to enjoy romantic relationships with his companions. He dressed in a Wild Bill Hickok fancy dress costume. After his regeneration, he battled with his old enemy, the Master, who was planning to steal his remaining regenerations. After many adventures, he died after a failed rescue attempt, the ship crashing into the planet Karn after its pilot refused help due to the Time Lord's involvement in the Time War. He was revived and was asked to help end the Time War. He reluctantly agreed and drank a special elixir to influence the character of his next incarnation; a warrior.

Companions:
 * Grace Holloway – A cardiologist from 1990s San Francisco.
 * Samantha Jones – A young woman from 1990s London.
 * Bernice Summerfield
 * Stacy Townsend – A young woman from the 23rd century, who worked aboard the Dreadnought
 * Ssard – An Ice Warrior from Mars.
 * Fitz Kreiner – A young man from 1960s London.
 * Izzy Sinclair – A young woman from 1990s Stockbridge.
 * Fey Truscott-Sade – An undercover agent from 1930s England.
 * Kroton – A Telosian Cyberman who retained his ability to feel emotions.
 * Gemma Griffin – A young woman from Folkstone, at an unspecified point in the future.
 * Samson Griffin – A young man from Folkstone, at an unspecified point in the future.
 * Mary Shelley – A writer from 19th century England.
 * Charlotte Pollard – A young adventuress from 1930s England, who lived when she should have died.
 * C'rizz – A Eutermesan from Bortresoye in the Divergent Universe.
 * Compassion – A human-turned-TARDIS from Anathema, who met the Doctor on 1990s Earth.
 * Miranda Dawkins – One of the last survivor's of a Gallifreyan catastrophe, adopted by the Doctor.
 * Anji Kapoor – A trader from 1990s England.
 * Trix MacMillan – A con artist from 2000s England.
 * Destrii – An Oblivioner from Oblivion, who met the Doctor on Ophidius.
 * Lucie Miller – A young woman from 2000s Blackpool.
 * Tamsin Drew – An actress from 2010s England.
 * Molly O'Sullivan – A VAD from 1910s Ireland.
 * Liv Chenka – A medical technician from 29th century Kaldor.
 * Helen Sinclair – A language scholar from 1960s England.
 * Josie Day – A living portrait, who the Doctor first met as a young painter in 2010s Wales.
 * Bliss - A quantum physics student.

The War Doctor
"No More"

- The War Doctor

Played by John Hurt

Created as a warrior, he fought in the Last Great Time War against the Daleks. He rejected his chosen title in order to fight in the Time War, only picking up companions if they were willing to fight. As he began life with a young appearance and ended up regenerating of old age, it is fair to assume that this may have been the most long-lived of all the Doctors, except for the First. The memories of this incarnation were rejected by his successors, who believed he ended the war by annihilating Gallifrey and therefore his own people along with the Daleks - something which he indeed came very close to, but ultimately didn't. In reality he joined all his incarnations and froze their home planet in a pocket universe, destroying the Daleks in the process. Because of the timelines were out of synch, he lost this knowledge until it caught up with the Eleventh Doctor. He regenerated from old age.

Companions:
 * The Squire – An agent of the Volatix Cabal, who was unbeknownst to this fact.
 * The Master – A Time Lord from Gallifrey, and one of the Doctor's oldest friends and enemies.
 * Rejoice – A leader of the Keskan people, who initially met the Doctor in her youth.
 * Kalan – A street-urchin from Rovidia.
 * Ollistra – A Time Lord Cardinal from Gallifrey, who was heavily involved in the Gallifreyan war effort.
 * Leela
 * Cinder – A resistance fighter from Moldox.

The Ninth Doctor
"Fantastic"

- Ninth Doctors Catchphrase

Played by Christopher Eccleston, 2005

Having regenerated after the Time War, the Ninth Doctor shows guilt of being the last surviving Time Lord, as he believed his previous incarnation destroyed Galifrey. Dressed in a black leather jacket and jeans, he finds a companion in Rose Tyler when he saves her from Autons, with Rose helping him defeating the Nestene Consciousness. He also discovered a lone Dalek who had survived the war. After a number of adventures, he met his end saving Rose from the energy of the Time Vortex, which she used to defeat a new Dalek empire.

Companions:
 * Rose Tyler – A young woman from 2000s London.
 * Adam Mitchell – A young researcher from 2010s England, who the Doctor met in Utah.
 * Jack Harkness – A time agent from the 51st century, who the Doctor met in 1940s London.
 * Tara Mishra – A 20th century UK UNIT lieutenant.

The Tenth Doctor
"Allons-y!"

- The Tenth Doctor

Played by David Tennant, 2005-10

Outwardly charming and charismatic, the Tenth Doctor wears a blue or brown suit with a brown overcoat, and various colored Converse All-Star sneakers. After battling the Sycorax, he lost a hand, but grew it back due to his recent regeneration. His saving of Queen Victoria from a Werewolf resulted in the creation of the Torchwood Institution. This Doctor also learns that the Master also survived the Time War, disguised as the human Professor Yana using a pocket watch to disguise his Time Lord biology. After Yana regains his true biology and regenerates into a younger body, the Doctor finds the Master posing as British Prime Minister Harold Saxon and defeats him, with The Master refusing to regenerate. Once more battling the Daleks, he aborts his own regeneration to only heal his wounds, and to avoid changing form, in the process channelling the energy to his severed hand, creating a half-human clone. He ultimately regenerates after he saves Earth from destruction by his own people, led by Rassilon, their President, with the Master saving his live and being trapped with Galifrey and the Time Lords in a pocket dimension, and then saving Mott by absorbing 500,000 rads of radiation, and holding it off long enough to visit his companions.

Travelling Companions: Allies and One-Time Companions:
 * Rose Tyler
 * Mickey Smith – A mechanic from 2000s London.
 * Martha Jones – A young physician from 2000s London.
 * Donna Noble – A temp from 2000s London.
 * Gabby Gonzalez – A young woman from 2010s New York.
 * Cindy Wu – A young woman from 2010s New York.
 * Anubis – An Osiran from Phaester Osiris, who joined the Doctor after a rejuvination.
 * Majenta Pryce – A time travelling hotelier from Vessica.
 * Emily Winter – An actress from 1920s Hollywood.
 * Matthew Finnegan – A young man from 1920s Hollywood.
 * Heather McCrimmon – A young woman from 2000s Edinburgh, and a descendant of Jamie.
 * Wolfgang Ryter – A young exchange student from 2000s Austria.
 * Sarah Jane Smith
 * Jack Harkness
 * Astrid Peth
 * River Song
 * Jackson Lake
 * Lady Christina de Souza
 * Wilfred Mott

The Eleventh Doctor
"Geronimo"

- The Eleventh Doctor

Played by Matt Smith, 2010- 2013

Dressed in a tweed jacket, bow ties and fezzes, the Eleventh Doctor meets Amy Pond as a child, helping her with a crack in her wall, taking her as a companion in the future. Encountering the Silence, an alien religious sect who want to prevent the Doctor's name to being revealed, he also marries River Song, a partial Time Lord who is the daughter of Amy Pond and Rory Williams. The Doctor then meets Clara Oswald in Victorian London, only for her to die during one adventure, but saves a modern-day version of her and takes her as a companion, and finds out he will die on Trenzalore. He then learns that his Time War incarnation didn't destroy Galifrey and the Time Lords, but saved them, with help from his previous incarnations. He then spends 900 years fending Trenzalone from many of his foes, while ageing into a very old man. With only Daleks left to fully defeat, he prepares to accept his foretold death, he's granted a new cycle of regeneration and channels some of the energy to destroy the Dalek invasion and becomes young again before regenerating.

Companions:
 * Amy Pond – A young woman from Scotland, who met the Doctor in 2010s Leadworth.
 * Rory Williams – A nurse from 2010s Leadworth.
 * Kazran Sardick – An heir to the skies of Sardicktown, whose past was changed by the Doctor.
 * Abigail Pettigrew – A woman cryogenically frozen as payment to Elliot Sardick, Kazran's father.
 * Kevin – A robotic Tyrannosaurus rex from Multiworld.
 * Alice Obiefune – A librarian from 2010s Hackney.
 * John Jones – A Chameleon musician, who the Doctor met in 1960s London.
 * ARC
 * The Squire
 * Abslom Daak – A criminal and Dalek Killer from 26th century Earth.
 * River Song – A human Time Lord archaeologist, who eventually married the Doctor.
 * The Sapling – A sapling generated by the Planting, with the memories of Alice and the Doctor.
 * Decky Flamboon – A Brancheerian from Sirus, who the Doctor met on Earth.
 * Clara Oswald – A nanny and English teacher from 2010s Blackpool.

The Twelfth Doctor
Played by Peter Capaldi

The first incarnation of a new regeneration cycle granted by the Time Lords when the Eleventh (and final) Doctor was about to die of old age on Trenzalore. He lost his companion, Clara Oswald, to the Quantum Shade, but was extracted from time by the Time Lords, who managed to bring Gallifrey back into the regular universe near the end of time. This Doctor was cunning, sarcastic and less affectionate that his predecessors. This incarnation took the form of an individual he had saved in his tenth incarnation.

Companions:
 * Clara Oswald
 * Courtney Woods – A young student from 2010s London.
 * Hattie Munroe – A lead singer and guitarist from the 40th century, who the Doctor met on the Twist.
 * Julie d'Aubigny – A swordswoman and opera singer from 17th century France.
 * Sonny Robinson – A comic book writer from 2010s England.
 * Val Kent – A comic book artist from 2010s England.
 * Jata – An Osumaran from Osumare, who the Doctor met in late 19th century Wyoming.
 * Jess Collins – An art history student from 20th century England.
 * Alex Yow – A photojournalist, and Brandon's sister.
 * Brandon Yow – Alex's brother.
 * River Song
 * Nardole – A humanoid turned cyborg, who the Doctor first met on 54th century Mendorax Dellora.
 * Bill Potts – A young university student from 2010s England.

Other Doctors
There have been numerous incarnations of the Doctor other than the thirteen official ones:
 * Two theatrical movies from the 60s were made starring a version of the Doctor played by Peter Cushing, which identified himself explicitly as Dr. Who, made no mention of being extraterrestrial and seems to have constructed the TARDIS from scratch. The first film has him traveling with two granddaughters, Susan and Barbara, and the second replaces Barbara with an older niece called Louise.
 * The Leader of the Republic of Great Britain in the parallel universe visited in Inferno was revealed in the novel Timewyrm: Revelation to be that universe's version of the Third Doctor. His appearance is based on a photo of Jack Kine, a special effects designer for the series.
 * During the mindbending contest between the Fourth Doctor and Morbius in The Brain of Morbius, several images are shown, including the Doctor's past incarnations and several unknown ones. It isn't clear if these additional images represent future incarnations of the Doctor, past or future incarnations of Morbius (who is also a Time Lord) or a mix of both.
 * The stage play The Seven Keys to Doomsday features the Third Doctor regenerating in an alternate Fourth incarnation played by Trevor Martin.
 * The Watcher was a humanoid manifestation of the Doctor who existed between his Fourth and Fifth incarnations and assisted the regeneration process. The exact nature of this phenomenon remains unclear.
 * The Valleyard is a manifestation of the Doctor's dark side which somehow came to life between his Twelfth and final form and confronted the Sixth Doctor. He also manifested himself in the Time Matrix with a false appearance in the identity of Mr. Popplewick.
 * In Battlefield, the Seventh Doctor is recognized (although not by his appearance) as the legendary figure from the Arthurian legends known as Merlin, and later confirms that Merlin's handwriting seems to be his own. However, he has no memory of it and speculates that it might refer to a future and/or alternate universe version of him.
 * The actor David Banks stood in as the Doctor in the play The Ultimate Adventure for two performances in 1989, replacing Jon Pertwee when he was feeling ill. Banks' Doctor was a unique incarnation wearing a brown hat and a Greenpeace T-shirt.
 * The character Muldwych from the New Adventures novel Birthright, is shown to represent a future incarnation of the Doctor and implied as a strong candidate for the identity of Merlin.
 * An unspecified version of the Doctor, seemingly from an alternative universe or timeline, serves as a member of the High Council of Gallifrey in the novel The Infinity Doctors.
 * A future version of the Doctor from the short story Good Companions was later featured in numerous written stories. He is described as very short with curly red hair, and wears an Afghan coat over a yellow waist-coat and white shirt, open-toed sandals and socks, and bracelets.
 * The comic relief special The Curse of Fatal Death introduces us to an alternative and parodic version of the Doctor Who universe, showing an original Doctor interpreted by comedian Rowan Atkinson, traveling with a companion named Emma. Through the special he regenerated multiple times, with the short-lived subsequent Doctors being portrayed by Richard E. Grant, Jim Broadbent, Hugh Grant and Joanna Lumley.
 * Similarly, Mark Gatiss played a comedic version of the character in the parody special The Web of Caves.
 * The Scream of the Shalka special featured an original incarnation of the Doctor, played by Richard E. Grant as a tall, pale man dressed in a long coat and traveling with a reformed Master whose conscience was transplanted to a robot body. This Doctor comments about a cat having used up his nine lives and adds: "rather like me", leading to the possibility that this is meant to represent the Thirteenth Doctor.
 * Another unspecified version of the Doctor was featured in the novella The Cabinet of Light, and later in the Time Hunter novel Child of Time, under the alias of "Dr. Smith" (but not at all related to the Lost in Space character).
 * Geoffrey Bayldon played an alternate universe version of the Doctor who never left Gallifrey in the Big Finish audio Auld Mortality and its sequels. This was the first story in the Doctor Who Unbound series, consisting exclusively of alternate universe stories.
 * An alternate version of the Third Doctor, with a different appearance chosen by the Time Lords and a different part of Earth chosen for his exile; was featured in the Unbound story Sympathy for the Devil and its sequel Masters of War; played by David Warner.
 * Another Unbound story, Full Fathom Five, features an evil version of the Doctor played by David Collings and Ian Brooker.
 * Finally, the Unbound story Exile shows a female version of the Doctor played by Arabella Weir, which regenerated from an incarnation played by Nicholas Briggs after that incarnation committed suicide.
 * Colin Baker played an aged and villainous alternate universe version of his Doctor which adopted the title of Lord Burner in the audio story Disassembled. In another audio story, Forever, Baker played "Commentator Theta Sigma", from yet another alternate universe. Both stories are part of Big Finish's Gallifrey audio series.
 * Similarly, Paul McGann played a parallel timeline version of the Eight Doctor which used the alias Johann Schmidt in the audio story Klein's Story.
 * Similar to the Valleyard, the Eleventh Doctor once met a manifestation of his dark side in the form of the Dream Lord.
 * In The Day of the Doctor an elderly Tom Baker appeared as a museum curator who is strongly implied to represent some version of the Doctor, possibly an aged Fourth Doctor from another timeline although this is merely speculation.