Previously in the author's fanfiction stories and Daily cartoons:
The Doctor's father was a renegade Time Lord geneticist, crossbreeding his own genes with members of other planet's peoples in an attempt to rejuvenate the tired Time Lord genome. The Doctor was his Father's half-human Time Lord.
Between the many dimensions in which Superman exists, the Doctor is known to date to have been his godfather, his best friend, his foster son, and one of his pre-cape-and-tights adolescent mentors.
The Doctor's time machine the TARDIS first landed on the starship Enterprise during Lieutenant Spock's service under Captain Christopher Pike, on the occasion of Pike's disastrous first contact with the Klingons which ultimately led to the decades-long conflict between the Klingons and the Federation and to the formation of the Federation Prime Directive. Some of the intelligence gathered by Spock into his report on the Doctor to Starfleet was classified captains'-eyes-or-higher only.
The first time the Doctor encountered his fellow renegade Time Lord the Master once the Master had assumed that title, the Master was attempting the conquest of Earth, having risen to power in an early twentieth century European country by assuming the identity of an Earthman, a paperhanger.
After his first regeneration the Doctor convinced Kirk and Spock of his identity by alluding to his first meeting with Spock. The word "ship" became an informal code word to indicate to the Enterprise officers when someone they didn't recognize was a new incarnation of the Doctor.
The Doctor's reaction when first confronted with a Harry Potter novel was, "J.K. Rowling?! I thought I asked her not to repeat my school stories!!"
The Doctor's encounters with Captain Kirk's Enterprise have often entailed loud arguments on the conflict between the Federation Prime Directive and the Doctor's more proactive philosophy.
During the Doctor's exile to 1970s Earth by the Time Lords, and during a time-travel mission by Captain Kirk to that time, the Doctor revealed to Kirk that the beings known to Federation archaeologists as the Preservers are not long-disappeared as the Federation believes them to be, and had at least two agents on twentieth-century Earth: Kirk's friend Gary Seven and the android Questor. The Doctor did not reveal that the so-called Preservers are really the Celestial Intervention Agency of the High Council of the Time Lords, but Captain Kirk figured it out anyway.
One of the first contacts made by the Doctor in the immediate wake of the rescinding of his exile was with the personnel of the 4077th MASH. Despite the surgeons' objections to his lack of official credentials, the Doctor was occasionally allowed, or forced by circumstances, to substitute for one or more of them in the hospital unit's operating room, to no yet recorded disaster.
Spock's ward Saavik, upon coming of age, became his bondmate in the wake of the dissolution of his bond with T'Pring.
The Doctor and Captain Kirk discovered the renegade Time Lord known as the Rani performing eugenics experiments on the entire population of a Federation protectorate world. The Federation took custody of much of her work and notes.
When the Doctor first met Darth Vader and Obi-Wan Kenobi, and Indiana Jones, he was in his fourth regeneration - but they had already met later regenerations of him. (The use of regeneration as a synonym for incarnation seems to be translation of a Gallifreyan idiom.)
The Enterprise officers learned about the Doctor's father when Saavik of Vulcan turned out to be one of his progeny - Saavik being half Time Lord rather than, as had been previously believed, half Romulan - at the time of her first regeneration during the Genesis crisis. Other heroes discovered or suspected by the Doctor to be his half-siblings include, but are not limited to, Wonder Woman, Angel's son Connor, and Anakin Skywalker.
The Doctor and Captain Kirk discovered that the world known to the Federation as Organia was, in reality, the Doctor's home planet of Gallifrey, during the era of the founding of Time Lord civilization by Rassilon.
When the Doctor's friend Brigadier Alistair Lethbridge-Stewart died he discovered he is one of the race of Immortals that includes Connor and Duncan Macleod. In the twenty-fourth century the Brigadier was a Starfleet admiral.
Involved in one of their cases early in the history of their team, the Doctor imposed on Special Agents Mulder and Scully a hypnotic amnesia relating to the full facts they'd learned about him, which he was able to reverse and reimplement at need with posthypnotic commands.
The Master learned he was one of the Doctor's Father's progeny. The Father had combined one of his Y chromosomes with an X of Londo Mollari, sometime Emperor of Centauri Prime - making Londo the Master's mother. But the Master's warped megalomanic filial affection to his newly-discovered "mother" so endangered the history of the Shadow War that Kosh removed all of the Master's memories of his discovery before anyone but Londo had been told.
When the Klingon-Cardassian Alliance of the so-called "mirror" universe plotted with the Master's help to invade the Federation, the Doctor brought a second "shadow" of Captain Kirk out of the Nexus to help Commander Sisko of DS9 to unite the rebellion against the Alliance.
On a fact-finding mission into the past with the Doctor's aid, Captain Picard of the Enterprise-D discovered that he was, as he had been told by Guinan and by Sela herself, responsible for the temporally paradoxical existence of the enemy Romulan commander Sela. Picard also learned that the Doctor is as well-known to Romulans as he is to Starfleet, and is responsible for something called the Tradition of Dorek. Some years later Sela enlisted the Doctor into her quest to rescue her timelost mother - originally one of Picard's officers - back to her native time.
When Lois and Clark Kent had a baby left on their doorstep, it developed that the baby was the Doctor, given to them to raise by his adult self.
The Doctor first met Buffy the Vampire Slayer when the Time Lords pulled her into her future - onto the Enterprise-E. In another adventure Buffy's sidekicks Willow and Xander learned that the Doctor has a history with Buffy's star-crossed lover the re-ensouled vampire Angel. In yet another, the Doctor learned for the first time that Buffy is his genetic mother. Buffy traveled in the TARDIS with the Doctor for a short time during the summer after her confrontation with the demon Acathla.
Sometime between the time of the Enterprise and of the Enterpise-D, Saavik went missing, and was rescued by the Doctor, but not before she was declared dead and Spock had rebonded. (Spock's new bondmate was his old flame the Romulan Commander of the cloaking device incident.) Upon Saavik's rescue she regenerated and became the Doctor's current girl traveling companion, not very long before he regenerated into his first ninth incarnation aboard the starship Voyager in the Delta Quadrant.
When Queen Amidala of Naboo was required by her planet's traditions to take a year-long sabbatical but the Jedi Council implored her not to be absent from her throne for so long, she became the Doctor's traveling companion after Saavik's departure from the TARDIS. After her year Amidala was returned by the TARDIS to the moment she'd left.
On the return of the starship Voyager to Earth, Captain Janeway and her Emergency Medical Hologram sued Starfleet for equal rights for holograms, the Doctor litigating their case. The court-martial ruled that some holograms are intelligent life forms.
In contradiction of his own history, the Doctor found his TARDIS landed on the starship Enterprise of Jonathan Archer, the century previous to Pike and Kirk. But he discovered several anachronisms, and he and Archer learned that someone from the not-yet-born Federation's future was waging a "temporal cold war" to change history in this era to the detriment of the Federation. The Time Lords are not unaware of this danger, but as always prefer to operate to maintain the integrity of the timeline through agents; including Archer's Vulcan officer T'Pol, and the Doctor who, in one incident involving the enemies' native-time agent Silik, was retrogenerated by a faulty time device back into his eighth incarnation.
Meanwhile, despite animosity between Earthmen and Vulcans in the era, Archer and his engineer Tucker both became romantically involved with T'Pol. Encouraged by the Enterprise's Denobulan medical officer Phlox, the three of them arrived at a mutually acceptable but discrete relationship.
Under the generalship of Captain Kirk (or of the shadow of Kirk which the Doctor retreived from the Nexus), the rebellion against the mirror-universe Klingon-Cardassian Alliance threw off the Alliance's yoke and established a republic in what had been Empire space.
After closing up the Hellmouth in Sunnydale and activating all the potential Slayers in the world thus nullifying her own "Chosen One" status, Buffy elected to travel for a time with the Doctor again, returning after more than a year of subjective time to the same moment in the summer of 2003 when she'd left with him.
Among the circumstances surrounding the Doctor's renegeration into his final ninth body was a meeting between Captain Kirk and Captain Archer, and the establishment of the Tradition of Dorek. The Doctor, Kirk and Archer discovered that Time Lord civilization is an organizational descendant of Starfleet. The Doctor discovered that he is the technological reincarnation of Rassilon, the founder of Time Lord civilization.
Though ordinarily the Doctor's friends such as the Brigadier or Captain Kirk experience his visits in the same chronological order he does (Obi-Wan Kenobi, Indiana Jones and Angel being known exceptions), for a time there was overlap of visits from the Doctor's eighth and ninth incarnations.
After the former Angel Investigations personnel successfully carried out Angel's plot to assassinate the most powerful demons in Wolfram & Hart and in Los Angeles at large, they were rescued by the Doctor. Offered "probationary" positions with Buffy's new Slayer society, they declined and took their fight back to the streets of L.A.
Unaware of the temporal effects of intergalactic Gate travel, Major Sheppard and the Stargate Command mission to Atlantis in the Pegasus galaxy arrived there in the era of their Clone Wars and the fall of the Galactic Republic.
During a mission with Major Sheppard's exploration team the Doctor took a fatal radiation blast for one of the SGC officers. When the teammember expressed a willingness to reverse the sacrifice the Master android performed on him for the Doctor the same lifeforce transfer as the Master performed on Tremas of Traken for himself in his first subsumption of another body after his Time Lord regeneration cycle was depleted. Though the Doctor appeared to have regenerated he was still in the ninth body of his normal regenerative cycle.
The Doctor's final regeneration spent her time saying goodbye to all her friends, ultimately enlisting the Emergency Medical Hologram to technologically reincarnate her as Rassilon.
Other heroes the Doctor has met include but are not necessarily limited to Nick Knight, Mal Reynolds, Dylan Hunt, Xena, John Crichton, Spider-Man, the Prisoner, Jack O'Neill, and the Earthman named Dr. Who who built a time machine into a police box.