Sixth Doctor

Regeneration
The Doctor regenerated after exposure to spectrox and contracting the fatal spectrox toxaemia disease on the planet Androzani Minor. He had given his companion, Perpugilliam "Peri" Brown the last of the antidote, leaving none left for himself. He remarked in his final moments that the regeneration felt "different this time". (DW: The Caves of Androzani)

Post-regenerative crisis
Following this regeneration, he suffered from a particularly unstable personality and even attempted to throttle Peri to death. The Doctor then decided to exile himself on Titan III, but soon got involved with stopping Mestor and his gastropods. On Titan III he also met another Time Lord, his old friend Azmael. Throughout, he experienced extreme lows to bouts of near-insanity and violence. (DW: The Twin Dilemma)

With Peri and Frobisher
After a short time, the Doctor's personality settled down into an extremely large ego with a side of compassion only experienced by his closest friends. He set out to fix everything wrong with his aging TARDIS and succeeded in fixing its broken chameleon circuit. For a brief time, it managed to change shape. (DW: Attack of the Cybermen)

Peri must have parted company with the Doctor for a short amount of time, however the Doctor stumbled upon Whifferdil Avan Tarklu, a private investigator set upon the Doctor as revenge by Josiah W. Dogbolter. Initially the Doctor's tormentor, Tarklu decided to travel with the Doctor, changing his name to Frobisher and his shape to that of a large, rather cartoonish penguin. (DWM: The Shape Shifter)

Peri and Frobisher would travel together with the Doctor for periods of time, between taking breaks from him.

The Prosecution
During an adventure on the planet Thoros Beta, the Doctor and Peri were forcibly separated by the Time Lords. Peri remained on the world in dire peril of having of the Mentor Kiv's mind transferred into her body. Meanwhile, a council of Time Lords forced the Doctor into his TARDIS and made the ship re-materialize in the Space Station Zenobia. (DW: Mindwarp)

The Valeyard (as he learned later, both enemy and, in some sense the Doctor himself) acted as prosecutor and an Inquisitor, Darkel. Because he had been taken out of time, the Doctor suffered from partial amnesia. He found himself once again on trial for interfering in the affairs of the universe. He elected to represent himself in the trial, for which he and his prosecutor, the Valeyard, would present events from his life as evidence via the Matrix. (DW: The Mysterious Planet, Mindwarp) The Doctor suffered a severe emotional blow as he witnessed the apparent destruction of Peri's mind and her physical death on Thoros Beta. (DW: Mindwarp)

Defense
After a recess, the Doctor would have the opportunity to present a case for defending himself, presenting an adventure from his own future, by which time he had met an Earth woman Melanie "Mel" Bush. The Valeyard seized on this as a chance to try the Doctor for the genocide of the Vervoids, prohibited by Article 17 of the Constitution. (DW: Terror of the Vervoids)

Aftermath
The Valeyard had falsified some of the evidence (which included the supposed death of Peri) with the aid of the High Council, in order to cover up a conspiracy which the Doctor had unknowingly uncovered. By this time, though, the Doctor had gradually won Darkel over to his side.

The Valeyard schemed to steal the Doctor's remaining regenerations with the help of the corrupt Council. Paradoxically (because in the Doctor's timeline, he had not met her yet) Mel was brought to the trial as a witness, as well as Sabalom Glitz. The Doctor's enemy, the Master, intervened. As the populace of Gallifrey reacted to news of the dishonesty of their High Council, they seemed ready to overthrow their leaders. Subsequently, Darkel suggested the Doctor as the new Lord President, but the Doctor suggested that Darkel herself would make for a better choice. The Doctor left in his TARDIS with Mel. The Valeyard, apparently killed inside the Matrix, had actually survived. (DW: The Ultimate Foe)


 * At some point the Doctor must return Mel to her original point in time following the conclusion of the trial. (MA: Time of Your Life)

Later travels
The Doctor travelled to Bianca's Bar and became involved in a problem concerning Iris Wildthyme. (BFA: The Wormery)


 * Following his trial, the Doctor appears to have become a more sombre individual. (DWM: Time & Time Again)

He spends some time on the planet Torrok, determined to become a hermit and avoid becoming the Valeyard, however is interrupted in this venture. He eventually meets a young man, Grant Markham. (MA: Time of Your Life)


 * At some point Grant departs from the Doctor.

The Doctor (at some point after his trial) was tracking nexus point distortion and encountered Evelyn Smythe. The Doctor then took her back in time to stablise the nexus point and save her life. (BFA: The Marian Conspiracy)


 * At some point Evelyn leaves the Doctor and settles down on the planet Vilag.

At some point after his travels with Evelyn but before meeting Mel, the Doctor picked up a distress signal from a desert island in the year 500,002. There he rescued a young girl named Charley Pollard who, unbeknownst to the Doctor, was, in fact, the companion of one of his later incarnations. (BFA: The Condemned)


 * At some point Charley leaves the Doctor.

The Doctor met Melanie Bush on a beach in Brighton in 1989. Mel was a computer programmer. She elected to travel with the Doctor for some time, until the end of the Doctor's sixth regeneration. (PDA: Business Unusual)

Characteristics
The Sixth Doctor is probably the most consistently arrogant, and certainly the most bombastic. He almost never doubted his own ability, and considered himself greatly superior to nearly everyone he encountered. This included his companions, especially Peri, though he seemed to have mellowed during his time with Evelyn. More than his other incarnations, the Sixth Doctor could be something of a fatalist, more than once deciding he was doomed and resolving to accept his fate.

Physically, he is very tall; Mel also considered him to be overweight, and forced him to take up both a diet (consisting mainly of carrot juice) and an exercise regime, neither of which he felt he needed.

Personality
The Sixth Doctor was unpredictable. Arrogant and self-absorbed, stubborn and childish, argumentative and tasteless, he could often be seen as unlikeable or even loathsome. This was a Doctor who did not suffer fools gladly; he sometimes seemed to endure his Companion's presence far more than he actually appreciated it, and held himself as superior to almost anyone he encountered. But the new incarnation's brash exterior hid the fact that this was a Doctor more determined than ever to defeat the evil he encountered. He was possessed of a tenacity and a thirst to do what was right that was far more visible than ever before. Despite his often unstable demeanour, he was always quick to act when the situation called for it, and very little -- even his Companions -- could hope to get in his way.

Habits and Quirks
The Sixth Doctor is very fond of cats, and always wears one of a number of cat-shaped pins or brooches in his possession. His taste in clothes is the subject of much ridicule, though it has been suggested that he wears his outlandish coat in order to distract people from noticing anything else about him.

Mysteries and Discrepancies

 * Why is he so much more erratic than the other Doctors immediately following his regeneration? Is spectrox toxaemia really so severe as to provoke such a reaction in a Time Lord?


 * Why does he leave with Mel at the end of his trial? Surely, even if he is taking her back to her proper place with his future self, wouldn't that flout the Laws of Time right under the Time Lord's noses?


 * Perhaps the Laws of Time work differently than the way we had assumed.


 * We have varying accounts of the reason for this Doctor regenerating into his next form besides a simple head injury.


 * The Doctor may have suffered a more serious injury which caused his regeneration.

Undocumented adventures

 * The Doctor had met Captain Travers previously. (DW: Terror of the Vervoids)

Key Life Events

 * The Doctor regenerates. (DW: The Caves of Androzani)


 * The Doctor re-unites with Jamie and encounters his own second incarnation. (DW: The Two Doctors)


 * The Time Lords put the Doctor on trial and he serves as his own defender. The Valeyard is his prosecutor and also his own possible future incarnation. (DW: The Trial of a Time Lord).


 * The Doctor regenerates. (DW: Time and the Rani)

Behind the scenes

 * According to Colin Baker his coat was created (the way it appears) because John Nathan-Turner had the idea that it should be in "very bad taste". (DWM: DWM Issue 118 - Colin Baker Interviewed)