Fourth Doctor

"It may be irrational of me, but human beings are quite my favorite species."

- The Doctor

Currently the longest running (after the Seventh Doctor and the Eighth Doctor) and typically thought of as one of the most popular doctors.

Independence
Having regenerated for a third time, the Fourth Doctor seemed to be in a hurry to leave Earth, but was eventually persuaded to stay and help Brigadier Lethbridge-Stewart deal with Think Tank and their K1 robot. The Fourth Doctor took Sarah Jane Smith and Harry Sullivan to travel with him in the TARDIS. (DW: Robot)

In the midst of another adventure, a Time Lord appeared to the Doctor and offered him a mission, to intervene in the creation of the Daleks, either to prevent it, or to induce the Daleks to develop into less dangerous creatures. (DW: Genesis of the Daleks)


 * This set into motion a series of events that would eventually lead to open war between Daleks and Time Lords and the destruction of Gallifrey.

Upon his return to Earth and the defeat of the Zygons, Harry decided to remain. (DW: Terror of the Zygons)


 * The Doctor had begun, even more so with this regeneration, to break his ties with Earth. Despite intending to resign from Unit (Pyramids of Mars), the Doctor never formally left his position as their unpaid scientific advisor. (DW: The Sontaran Stratagem'')

Return to Gallifrey
After many adventures together, the Doctor received a telepathic summons from Gallifrey and returned Sarah to Earth (DW: The Hand of Fear), though mistakenly, not to her home in South Croydon but to Aberdeen. (DW: School Reunion).

On Gallifrey, the Doctor defeated the Master and renewed his acquaintance with his former teacher Borusa. He also re-experienced, to his disgust, the decadence of Time Lord civilization. (DW: The Deadly Assassin).


 * The Doctor travelled for an unknown period of time alone.

New friends
Visiting a nameless jungle world, he made the acquaintance of Leela of the Sevateem. (DW:The Face of Evil)

Lord President of Gallifrey
Returning once more to Gallifrey and, posing as vainglorious and power-mad, sought and attained the office for Lord President as part of a scheme to save his home world from an invasion force of two separate enemies, the Vardans and the Sontarans. Leela decided to remain on Gallifrey with Andred, a Gallifreyan in the Chancellory Guard and K-9. However, the Doctor left the Capitol with a duplicate K-9, Mark II, in a crate (DW: The Invasion of Time).


 * The Doctor and K-9 Mark II spent an indeterminate period of time together.

Quest for the Key to Time
The White Guardian summoned the Doctor to initiate a quest to locate and assemble the segments of the Key to Time. For this purpose, the White Guardian introduced him to a new companion, Romana (DW: The Ribos Operation).The Doctor and Romana located, assembled and disassembled the Key, and to escape the wrath of the White Guardian's opposite, the Black Guardian, the Doctor installed a randomiser in the TARDIS console (DW: The Armageddon Factor). Afterwards, Romana regenerated (DW: Destiny of the Daleks), and the two, along with K-9, continued to travel together.


 * The Doctor, Romana and K-9 Mark II spent an indeterminate period of time together, potentially quite long given the Doctor and Romana's longevity as Time Lords.

E-Space
After spending some time trapped in a pocket universe called E-Space (DW: Full Circle), during which Romana and K-9 left (DW: Warriors' Gate) and Adric joined (DW: Full Circle), the Doctor entered into battle against The Master, who had reconstituted himself. While struggling with his enemy, the Doctor he fell off the Pharos Project radio telescope down to the ground hundreds of feet below. The mysterious entity known as The Watcher, which had been tracking him through time and space, then merged with him and he regenerated. (DW: Logopolis)



Appearance
In stark contrast to the elegant, refined figure of his third incarnation, the Doctor was an unkempt, awkward-looking figure, dressed in battered clothing and an impossibly long multi-coloured scarf, knit for him by Madame Nostradamus. (DW: Robot). His dark curly hair was often partially hidden by a large floppy hat.

Age
In more than one episode during season 13, the fourth Doctor states his age to be 749 years (DW: Seeds of Doom, Part One).

Personality
"I'm a very dangerous fellow when I don't know what I'm doing."

- The Doctor.

This incarnation was most definitely not Human, and stood apart from others, even most of his own people. (DW: The Deadly Assassin, The Invasion of Time)

When Sarah upbraided him over his callousness at the sight of a man killed by the animate corpse of his own brother, the Doctor reminded her of the larger issue of stopping Sutekh. (DW: Pyramids of Mars). His mind is five leaps ahead of anyone, including himself; only Romana seemed able to keep up with the Doctor's trains of thought. He delighted in keeping both friends and foes alike off guard with oddball humour and curious pranks, as in his second incarnation. Although generally peace-loving and kind-hearted, as per most of his other incarnations, the Doctor could also react with sudden violence when necessary; he was also not against taking a life in extreme circumstances (DW: The Brain of Morbius).

He could judge character keenly, almost instantly whether knowing who to trust or seeing through Unstoffe's faux guilelessness (DW: The Ribos Operation). Out of all the Doctor's selves, this incarnation had perhaps the most consistently anti-authoritarian attitude, having little tolerance for religious dogma (DW: The Brain of Morbius, Underworld) or nationalism (DW: Robot, The Armageddon Factor). The Doctor often played the fool to lull his opponents, such as Count Scarlioni, into underestimating him (though it did not work in that case.) But he was also a very intense, brooding individual, at times displaying a seriousness and fury belying his usually whimsical attitude, such as when telling the scientist Sorenson that he must put right what he done wrong, even if he must sacrifice his life to do so (DW: Planet of Evil).

Unlike his third incarnation, this Doctor did not have a close working relationship with UNIT or The Brigadier, reacting with anger when UNIT recalled him to Earth (DW: Terror of the Zygons). Except for this and a handful of other occasions, the Doctor kept his distance from UNIT (even at the expense of abandoning his predecessor's beloved roadster, Bessie), and later incarnations have never reestablished the same rapport that existed between the Doctor and UNIT before his fourth incarnation.

Habits and Quirks
Souvenirs from many different worlds littered his pockets. (DW: Robot, Genesis of the Daleks). He would sometimes relax by playing with a yo-yo and liked to drink ginger beer (DW: The Android Invasion).

He would often have with him and offer jelly babies as a greeting. In his later life he developed a great fondness for tinkering about in the TARDIS. He relied upon his sonic screwdriver at least as much as in his previous incarnation.

He was also not adverse to winding up his companions on occasion; such as once fooling Leela into standing and playing with a yo-yo for an extended period of time, with her believing it was an experiment. (DW: The Robots of Death) On another occasion, he caused Romana to nearly panic when he pretended to become possessed by the Black Guardian (DW: The Armageddon Factor).

Unrecorded adventures

 * Presumably by himself, the Doctor visited Leela's home planet, encountered the supercomputer Xoanon and inadvertently installed in him a program copied from his own personality (DW: The Face of Evil).


 * ''We do not know at what time in the Fourth Doctor's life this event could have occurred or the reason why, later, he would fail to remember his adventure. One theory for the amnesia explains that this adventure as happening very early in his life, when he still suffered from post-regenerative trauma, possibly during the incident described below when he temporarily leaves following his regeneration.


 * In the first episode of the fourth Doctor, Robot, he is delirious from his regeneration and placed in a UNIT sickbay. He escapes in the TARDIS, appearing to abandon Sarah Jane on Earth. He then returns, a little more stable.


 * There are conflicting accounts surrounding some of the Doctor's activities circa 1979 involving Professor Chronotis, due to an incomplete surviving record of the events (DW: Shada) which may have been due in part to the Doctor being briefly abducted by Borusa's timescoop at around the same time (DW: The Five Doctors). Whether these events actually occurred, occurred in a different timestream, or in fact occurred to an later incarnation (Shada (webcast)) remain unknown.


 * There are at least three occasions in which extensive gaps may exist in the "historical record" of the fourth incarnation's adventures: between his first defeat of the Master on Gallifrey (DW: The Deadly Assassin) and Leela joining (DW: The Face of Evil); between the defeat of the Sontaran invasion of Gallifrey (DW: The Invasion of Time) and his encounter with the White Guardian (DW: The Ribos Operation); and between the defeat of Soldeed (DW: The Horns of Nimon) and the TARDIS arriving at Brighton Beach (DW: The Leisure Hive). (The Chronotis affair is one event that may have occurred within this last interval (DW: Shada, along with the Doctor's abduction to the Death Zone on Gallifrey (DW: The Five Doctors.)

Key Life Events

 * The Doctor regenerates. (DW: Planet of the Spiders, Robot)
 * Gains a new companion in Harry Sullivan and drives Bessie for the last time until his seventh incarnation. (DW: Robot)
 * The Doctor tries to prevent the creation of the Daleks and first encounters Davros. (DW: Genesis of the Daleks).
 * The Doctor and the Brigadier work together for the last time before the Brigadier's retirement. (DW: Terror of the Zygons). Soon after, he discontinues his active involvement with UNIT (DW: The Android Invasion and DW: The Seeds of Doom)
 * Harry Sullivan departs and returns to UNIT (DW: Terror of the Zygons) though he briefly reunites with the Doctor soon after (DW: The Android Invasion).
 * Sarah Jane Smith leaves (DW: The Hand of Fear) and the Doctor returns to Gallifrey, where he defeats the Master (DW: The Deadly Assassin). Afterwards, he travels alone for a time.
 * Gains a new companion in Leela and sets out to be Professor Henry Higgins to her Eliza Doolittle (DW: The Face of Evil).
 * Obtains his first robotic companion, K-9. (DW: The Invisible Enemy).
 * The Doctor assumes the office of Lord President on Gallifrey, fights back two invasions. Afterwards, Leela and K-9 choose to stay on Gallifrey; the Doctor begins assembling a second K-9. (DW: The Invasion of Time)
 * The White Guardian puts the Doctor on his quest to find the Key to Time and introduces him to Romana, who is assigned to him as a new companion. (DW: The Ribos Operation) Once defeated, the Black Guardian swears revenge. (DW: The Armageddon Factor).
 * The Doctor temporarily installs a randomizer into the TARDIS, intentionally making the vehicle's travels unpredictable. (DW: The Armageddon Factor)
 * Romana chooses to stay with the Doctor rather than return to Gallifrey, and regenerates into a new body. (DW: Destiny of the Daleks)
 * The Doctor removes the randomiser. (DW: The Leisure Hive)
 * En route to Gallifrey the TARDIS crew find themselves in E-Space where they find a new companion, Adric (DW: Full Circle).
 * Romana and K-9 leave the Doctor before he returns to N-Space. (DW: Warriors' Gate)
 * After gaining two new companions, Nyssa and Tegan Jovanka, the Doctor regenerates while saving the universe from a new incarnation of the Master. (DW: Logopolis)