Fourth Doctor

The Fourth Doctor was the fourth incarnation of the Time Lord known as the Doctor. He left all ties of his former exile behind on Earth before setting off to travel the cosmos, initially with Sarah Jane and Harry; Harry left on his own while the Doctor left Sarah Jane behind. During his travels with Sarah Jane, the Doctor gained a new companion in the robot dog, K-9, whom he had three models of.

After they departed, he travelled with Leela of the Sevateem until he stopped Gallifrey from being invaded and she stayed behind. Upon the White Guardian's orders, the Doctor began looking for the Key to Time with a fellow Time Lord Romana, whom he shared many enjoyable adventures with in her next incarnation.

During his travels in E-Space, the Doctor gained a new companion in Adric, a mathmatical genius while Romana and K-9 stayed behind when the two of them departed for N-Space.

While attempting to get the Chameleon circuit fixed, the Doctor gained two new comapnions in Nyssa and Tegan, who helped him prevent the Entropy of the universe along with the Master's reluctant aid.

The Doctor regenerated for the fourth time after falling from the Pharos Project telescope after preventing the Master from blackmailing the universe into seritude.

Premature Debut
The Third Doctor first regenerated after he fell of a roof during a struggle. However, the Nurazh attempted to take over the Doctor's mind, but, unable to cope with two Time Lord minds at the same time, perished, thus healing the Doctor back to his third incarnation. Jo Grant saw the Fourth Doctor long enough to describe him to the Third Doctor. (ST: The Touch of the Nurazh)

Post-regeneration
The Doctor's third incarnation regenerated some time after the radiation from theGreat One's lair took effect upon him. He returned to Earth to end his time in the company of Sarah Jane and the Brigadier after being lost in the Time Vortex for an unknown amount of time. K'anpo Rimpoche arrived and gave the Doctor a push for his regeneration, which he warned would scramble his mind. (DW: Planet of the Spiders)

Once he had regenerated, the Doctor suffered delirium, mumbling random things from his adventures, and was physical exhausted. He was put in sickbay, where Harry Sullivan kept watch on him. However, the Doctor managed to outwit him and get to the TARDIS to choose his new wardrobe. Though he still had a hard time realizing things around him, the Doctor was asked by the Brigadier to help deal with Think Tank and their K1 robot, which had gone insane from so many contridictory orders its programming should have prevented it from doing. Afterwards, he took Sarah Jane Smith and Harry Sullivan to travel with him in the TARDIS, unofficialy abandoning his laboratory. (DW: Robot)

Independence
The Doctor's first trip with his companions was an accidental one due to Harry messing around with the console controls. The TARDIS landing on Space Station Nerva, where humanity had been cryogenicly suspended to await Earth]'s natural resources to replinish. However, the [[Wirrn posed a threat as they wished to use the humans as foot and incubators for their kind. Luckily, a human converted in a Wirrn, retained his humanity and tricked the Wirrn into a suicide. On behalf of the space station, the Doctor went down to Earth with Harry and Sarah Jane to fix the relay. (DW: The Ark in Space)

However, once there, he found the Sontarans and quickly dealt with them to ensure humanity could resettle on Earth without fear. Fixing the relay allowed the Doctor to return to the space station and retreive the TARDIS to continue his travels with Harry and Sarah Jane. (DW: The Sontaran Experiment)

Whilst in the midst of traveling, a Time Lord appeared to the Doctor and offered him a mission: to intervene in the creation of the Daleks. He was either to prevent it, or to induce the Daleks to develop into less dangerous creatures. Although he was morally unable to commit genocide by destroying the entire race, he did manage to delay their advancement. (DW: Genesis of the Daleks)

Some time in the future, the Doctor had teleported himself, Harry and Sarah Jane to Space Station Nerva after departing Skaro. While waiting for the TARDIS to catch up with them, the Doctor becomes involved with stopping a Cyberman attack on Voga, the planet of gold. He ultimately stopped them from blowing it up and saved Sarah Jane from a fatal bite of a Cybermat. (DW: Revenge of the Cybermen)

Upon being contacted by the Brigadear to return to Earth for assistance (something that angered the Doctor as he hated to work), the Doctor encountered the Zygons and helped defeat them. Though the Doctor offered him a quick lift back home, Harry decided to end his travels with the Doctor. (DW: Terror of the Zygons)

The Doctor had begun, even more so with this regeneration, to break his ties with Earth. However, despite intending to resign from UNIT, (DW: Pyramids of Mars) the Doctor never formally left his position as their unpaid scientific adviser; other scientists had to be hired to take his place during his absence. (DW: The Sontaran Stratagem, Planet of the Dead)

adventures with Sarah Jane
Soon after Harry's departure, the Doctor and Sarah encounter anti-matter monsters. (DW: Planet of Evil) Attempting to return to UNIT, the Doctor had to prevent the last of the Osirians, Sutekh, from escaping his prison pyramid on Mars and bringing destruction to the Universe. Though unsuccessful in stopping Sutekh's release, the Doctor was able to defeat him by ageing him for 4000 years, ageing him to death. (DW: Pyramids of Mars)

Taking a trip back to present day Earth, the Doctor seemingly found himself in a town Sarah Jane had previously visited, only to find it was a facsimile populated by androids under the control of the Kraals. The Kraals own world had become uninhabitable, leading them to plan on wiping Earth's population out with a virus, then populating the planet themselves. The Doctor stopped them with the help of UNIT. (DW: The Android Invasion)

The TARDIS was next forced to land on Karn by the Time Lords to prevent the return of Morbius. The Doctor stopped the Frankenstein-esque resurrection of Morbius, but nearly died as a result. The Sisterhood of Karn used the Elixir of Life to heal him. (DW: The Brain of Morbius)

Soon after, the Doctor helped stop a Krynoid victim from taking over the Earth with plants, with the help of UNIT once again. This would be his last direct encounter with UNIT for many years. (DW: The Seeds of Doom)

During a trip in space, the Doctor accidentally brought Helix Intelligence to Italy in Earth's past, where it planned to dominate the human race by using a cult as its agents. The Doctor was able to stop this by reversing the energy flow, which drained the servants of the energy they were given, killing them in the process, but saving Earth. (DW: The Masque of Mandragora)

Later, the Doctor and Sarah Jane ended up in a quarry, where an explosion nearly cost Sarah her life. The Doctor found she obtained a petrified hand in the rubble and was possessed by Eldrad, who forced Sarah to take it to a nuclear power station, where it regenerated into a rock-based humanoid. The Doctor complied with Eldrad's request to be taken back to Kastria, where it is revealed it went mad and caused the end of his species; it planned to rule Earth, but the Doctor managed to trip him into a pit. (DW: The Hand of Fear)

Return to Gallifrey
After many adventures together, the Doctor received a telepathic summons from Gallifrey and returned Sarah to Earth, though, mistakenly, not to her home in South Croydon. (DW: The Hand of Fear) She would later tell him that he had actually left her in Aberdeen. (DW: School Reunion)

Upon return to Gallifrey, the Doctor tried to prevent the death of the Lord President, but was unsuccessful, ending up getting the blame instead for his murder. The Doctor put off execution by announcing his own candidacy for Lord President, buying him enough time to find a degenerated Master was responsible. Defeating the Master, the Doctor left his former teacher Borusa in charge. Throughout the adventure, he also re-experienced, to his disgust, the decadence of Time Lord civilisation. (DW: The Deadly Assassin)
 * The Doctor travelled for an unknown period of time alone following his departure from Gallifrey.

New friends
The Doctor returned to a planet he had visited centuries before. During his previous visit, he had accidentally imprinted his own mind on a human colony ship's powerful computer, Xoanon, leaving it with multiple personalities.

On his second visit to the colony planet, the Doctor was remembered as an evil god by the descendants of the colonists. Descendants of the colonist's "survey team" had become a warrior tribe called the Sevateem, while descendants of the technicians had become a technologically advanced tribe called the Tesh. After the Doctor cured the computer, one of the Sevateem, Leela, joined him on his travels. (DW: The Face of Evil) The Doctor brought the intelligent but uneducated Leela to many locations in human history, teaching her about science and her own species' past. In Victorian London, the pair encountered the magician Li H'sen Chang and his master, the self-styled Weng-Chiang, the latter of whom was actually the 51st century criminal Magnus Greel. (DW: The Talons of Weng-Chiang)

The Doctor, having become the host of the Nucleus, travelled to the Bi-Al Foundation medical centre in the year 5000, where its Swarm spread further. The Nucleus brought itself out of the Doctor's body and into the macro world to hatch more young. The Doctor travelled to Titan Base, where a hive of Swarm lay. The Doctor mixed the oxygen canisters with the methane atmosphere of Titan, blowing up the base. While there, he brought along Professor Marius' dog K9 to fight the Swarm-infected humans.

Unable to return to Earth with K9, Marius gave the Doctor K9 as a gift. (DW: The Invisible Enemy)

The Doctor later traces the source of a Time Hole to where a group of scientists have been experimenting on a skull called Eustace. Much to his horror, the Doctor finds that "Eustace" is actually the skull of a Fendahl Golden Core, but manages to stop a cult from nearly causing the end of the world. He later tosses the skull into a star to be rid of it and its evil once an for all. (DW: The Image of Fendahl)

The Doctor later helped the people of a Pluto colony repel against The Company that was oppresing them with high taxes, even saving a person from commiting suicide. (DW: The Sun Makers)

Some time later, the Doctor helped what remained of the original Minyans locate their race bank and home planet. He also defeated the Oracle, a machine that had been selfishly ruling the planet in place of its populace. (DW: Underworld)

Lord President of Gallifrey
Returning once more to Gallifrey and, posing as vainglorious and power-mad, the Doctor sought and attained the office of 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 K9 and Andred, a Gallifreyan in the Chancellory Guard she had fallen in love with. However, the Doctor left the Capitol with K9 Mark II, in a crate, planning to continue adventures with his beloved dog. (DW: The Invasion of Time)
 * The Doctor and K9 Mark II spent an indeterminate period of time together. However, in the next episode, DW: The Ribos Operation, he appeared to be activating K9 Mark II, giving the impression that no significant time had elapsed since leaving Gallifrey, though he could have possibly been repairing him.

Battle with the Hornets
While travelling on his own, the Doctor took up sojourn in a cottage in Sussex called Nest Cottage in the 21st century investigating a string of murders and picked up a dog called Captain. He found the murders were caused by stuffed animals animated by alien hornets, who wanted to invade the Doctor's mind. The Doctor brought the hornets towards Nest Cottage, where the TARDIS' dimensional stabilisers put up a force shield to prevent them getting out and taking over the world. (AG: The Stuff of Nightmares)

The Doctor travelled back to 1932 Cromer where he found Ernestina Stott under control of some ballet shoes owned by Mrs Wibbsey, both under influence by the hornets. The hornets attempted to shrink the Doctor and Ernestina down, putting them inside a doll's house filled with deadly dolls, but the Doctor escaped and found a way to bring them back to normal. He confiscated the doll's house and the ballet shoes and placed Wibbsey under his protection in Nest Cottage as his housekeeper and regularly mesmerised her to prevent the hornets from taking over her mind. (AG: The Dead Shoes)

He put an advertisement in a magazine to invite Mike Yates into his investigation of these hornets and keep him up to speed. (AG: The Stuff of Nightmares)

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 I. (DW: The Ribos Operation)

While the Doctor and Romana searched for the Key, they were twice interrupted by outside sources emitting chronometric radiation that disrupted the tracer's ability to work, in the form of a chronometric pulse caused by a breach in the higher dimensions (PDA: Tomb of Valdemar) and a network of spatial teleportation paths created by a malfunctioning time cabinet intersecting with Earth's ley lines. (MA: The Shadow of Weng-Chiang) After these two encounters, the Doctor and Romana took a long break from searching for the key. (PDA: Heart of TARDIS)

During this break, the Doctor, Romana, and K9 encountered a Frog-like being named Bolog, who had a fleet of ships at his command. The Doctor was able to stop him with a Banana. (DWM: Death to the Doctor!)

Later, the Time Lords contacted him, telling him that they needed him to go on a mission. The Doctor, however, left them after relearning that the Brigadier was in danger, after he was captured by a terrorist group. The Doctor discovered an Avatar universe that had the Second Doctor, Jamie McCrimmon, and Victoria Waterfield trapped inside. Afterwards, they were forced to continue with the quest. (PDA: Heart of TARDIS)

The Doctor and Romana finally 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 with the help of the Key while it was assembled. (DW: The Armageddon Factor) Afterwards, Romana regenerated (DW: Destiny of the Daleks) and the two, along with K9, continued to travel together.

Romana II
Forgetting Romana was only to be with him for the quest for the Key, the Doctor decided to bypass the randomiser and take himself and Romana on a relaxing holiday to Paris in 1979. There, the Doctor discovered that a Jagaroth named Scaroth had been splintered into twelve selves throughout time after his spaceship exploded, which led to the creation of life on Earth through the radiation from the exploding ship that effected the primordial ooze. The Doctor, Romana and detective Duggan succeeded in stopping Scaroth from preventing his spaceship from exploding, which would have undone life on Earth. (DW: City of Death)

The Doctor later received a distress signal and arrived on Chloris, a lush and verdant world with only small quantities of metals, all of which were controlled by its ruler, Lady Adrasta. The Doctor was sent for execution, but managed to avoid it, deciding to investigate the creature he was supposed to be fed to. He found it to be an imprisoned Tythonian that had been sent by its people to set up a trade agreement with Chloris. Deciding to end Adastra's tyranny, the Doctor allowed the Tythonian to kill her and let a new reign of peace be set up between the two species the planet. (DW: The Creature from the Pit)

The TARDIS then arrived on the space liner Empress, which has become locked together with a private ship, the Hecate, after colliding with it upon emerging from hyperspace. The Doctor and Romana met Tryst, who had a Continuous Event Transmuter machine. However, some Mandrels from Eden had somehow gotten onboard. The Doctor later discovers he has been lied to and the supposed addictive drug vraxoin was actually a valuable material that the Mandrels decompose into. The Doctor thwarted the plan of Tryst and the pilot of the Hecate, separated the two ships and returned the Mandrels to Eden. (DW: Nightmare of Eden)

Whilst in the middle of conducting TARDIS repair, the Doctor and Romana were caught in the middle of a sacrificial ceremony for a "god" called the Nimon. They discovered that this "god" was actually a parasite alien preparing Skonnos for the rest of its species. The Doctor succeeded in preventing the teleport from bringing more than two extra Nimon before the Nimon killed themselves as an accidental side-effect to their final gambit. With the help of the Anethans originally sent to be life-force sacrifices for the transporter, the Doctor destroyed the remaining Nimon before departing with Romana. (DW: The Horns of Nimon)

Tired of his constant unknown travels the Doctor took a break in Brighton Beach, but landed in wrong season to do so. At Romana's urging for a technologically advanced place of relaxation, the Doctor took them to the Leisure Hive, where the remaining Argolians run it. However, during the adventure to repair a rejuvenation machine, the Doctor ended up ageing hundreds of years. A genetically created Argolian named Pangol decided to take over, but thanks to the Doctor's interference, his plan to create a clone army of himself backfired as the Doctor was in the machine beforehand, gaining his youth back. However, the Doctor had to remove the randomiser in order to repair the machine, deciding that he had enough of running. (DW: The Leisure Hive)

Arriving on Tigella after repairing K9 from their previous adventure/vacation, the Doctor and Romana found themselves trapped onboard the TARDIS in a time loop while the last of the Zolfa-Thurans, Meglos. It also took the Doctor's form after attaching itself to a humanoid body to help itself steal the power of Dodecahedron. However, the Doctor was successful in redirecting the death beam Meglos had pointed at Tigella back on him after escaping the time loop. (DW: Meglos)
 * The Doctor, Romana and K9 Mark II spent an indeterminate period of time together, potentially quite a lengthy one given the Doctor and Romana's long life span as Time Lords.

Travels in E-Space
While trying to return to Gallifrey to take Romana back and reunite with Leela, the Doctor was taken by surprise when the TARDIS entered a pocket universe called E-Space. During this time, the Doctor picked up a new companion, Adric, who was nearly just as intelligent as he is. (DW: Full Circle) The Doctor eventually found a way to leave E-Space through a new opening at zero coordinates, but to his displeasure, Romana chose to stay behind to help liberate enslaved Tharils with K9. (DW: Warriors' Gate)

Back home
Following his return from E-space with Adric, the Doctor was in an increasingly morose and in a dark mood due to missing Romana. He was called by the Traken Union's Keeper to assist him in keeping evil away while his power waned from age and a replacement Keeper was found. The Doctor was successful in preventing the still decaying Master from obtaining ownership of the Source, but was unable to prevent him from stealing the body of Councillor Tremas. (DW: The Keeper of Traken)

Tired of the TARDIS' chameleon circuit being stuck as the police box, the Doctor decided to measure one and give the numbers to the people on Logopolis to fix it. However, he was impeded in his task by the newly reborn Master and was temporarily shrunk down along with the TARDIS due to a mathematical error. However, this error was quickly rectified and the TARDIS was reborn, minus the still malfuctioning chameleon circuit. During the fight, he picked up two additional companions, Tegan Jovanka and Nyssa. Much to the Doctor's horror, the Master had stopped all computations on Logopolis for too long; the universe had needed Logopolis to survive past its natural end and CVEs were the only thing allowing the universe to continue. The Doctor decided to form a shaky alliance with the Master to use the Pharos Project Radio to open a new CVE and save the universe. (DW: Logopolis)

Death
Despite having saved the universe, the Doctor knew the Master would try to make the situation work for him and was correct when he found the Master was going to blackmail the universe into servitude in exchange for its continued existence. Successful in making the CVE permanently open, the Doctor fell from the Pharos Project radio telescope to the ground, hundreds of feet below after disconnecting a wire. Though his companions were greatly worried about him, the Doctor told them the moment had been prepared for. The Watcher, which had been tracking him through time and space and was an apparition of his next incarnation, merged with him and the Doctor regenerated.

For a list of Fourth Doctor stories in the order in which he experienced them, see Fourth Doctor - Timeline.

Unrecorded adventures

 * Presumably by himself, the Fourth Doctor visited Leela's home planet, encountered the supercomputer Xoanon and inadvertently installed in him a copy of his own personality. (DW: The Face of Evil)
 * After his regeneration the Fourth Doctor was delirious and placed in a UNIT sickbay. He escaped to the TARDIS, which he was seen to activate. It appears, however, that he never actually dematerialised.
 * There are conflicting accounts surrounding several of the Fourth Doctor's activities during the Shada crisis. (DW: Shada) These discrepancies arises out of Borusa's interference with the Doctor's timeline (DW: The Five Doctors). Whether these events actually occurred following the events of the Fourth Doctor's abduction or whether these events happened to the Eighth incarnation, remain unknown. (WC: Shada)
 * The Fourth Doctor attended the funeral of Alistair Gordon Lethbridge-Stewart. (ST: The Gift)
 * The Fourth Doctor and Azmael had an encounter in which Azmael drank so much that the Doctor had to throw him into a pool to sober him. (DW: The Twin Dilemma)
 * The Fourth Doctor met Winston Churchill in 1879, posing as a Punch and Judy man whilst hunting Cybermats. (REF: The Brilliant Book 2011)

There are at least three occasions in which extensive gaps may exist in the "historical record" of the fourth incarnation's life:


 * 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)
 * Though the implication is that there was not a significant amount of time between these two stories.


 * Between the defeat of Soldeed (DW: The Horns of Nimon) and the TARDIS arriving at Brighton Beach. (DW: The Leisure Hive)


 * The events at St Cedds College (DW: Shada) along with the Doctor's abduction to the Death Zone on Gallifrey (DW: The Five Doctors) may have occurred during this period.

Age

 * While on Earth, the Doctor stated his age to be 749 years. (DW: The Seeds of Doom)
 * After ageing four years from crossing a split in time, the Doctor said: "I shall still think of myself as 743 ... or was it 730, I never can remember..." (DWM: The Time Witch)
 * See separate article.

Personality
The Doctor's fourth incarnation was most definitely not human-like in nature, and he stood apart from others, even most of his own people. (DW: The Deadly Assassin, The Invasion of Time)

The Doctor was known to be aggressive as when the Krynoid pods came to Earth (DW: The Seeds of Doom)

When Sarah upbraided him over his callousness at the sight of Laurence Scarman killed by the animated corpse of his own brother, the Doctor reminded her of the larger issue of stopping Sutekh. (DW: Pyramids of Mars) His mind was often leapt ahead of anyone, including himself. 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 were most of his 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, The Ribos Operation), but in their first adventure, scolded Leela multiple times for unnecessary killing. (DW: The Face of Evil)

He told the mutating Sorenson that the results of his experiments were his own fault and took no action to help him and proceeded to throw him into the pool of Anti-matter. He did however rescue Sorenson when the process was reversed. (DW: Planet of Evil)

He could judge character keenly, almost instantly whether knowing whom to trust or seeing through Unstoffe's false guilelessness. (DW: The Ribos Operation) Of all of the Doctor's incarnations, this one had perhaps the most consistently anti-authoritarian attitude, with little tolerance for religious dogma (DW: The Brain of Morbius, Underworld, The Stones of Blood, The Power of Kroll) 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 Count Scarlioni's specific case. (DW: City of Death)

Despite his charm and offbeat humour, the fourth incarnation was arguably more aloof and sombre than his previous incarnations. He could be intensely brooding, serious and even callous, and would keenly scrutinise his surroundings even when playing the fool. He would be furious with those he saw as stupid, frivolous, misguided or evil. When taking charge, he could be considered authoritative to the point of egocentricity, but he was usually the only one capable of solving the situations he found himself in. He generally maintained his distance from the Time Lords, even after they had lifted his exile, and resented that they were capable of re-entering his life when they deemed it necessary. Not only did he seem more inclined toward a solitary existence, (DW: The Deadly Assassin) he also emphasised his distance from humanity, although he stated on more than one occasion that he found mankind to be his favourite species. (DW: The Ark in Space)

Unlike his third incarnation, this incarnation 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. Later incarnations never re-established the same rapport that existed between the Doctor and UNIT before his fourth incarnation, although his tenth incarnation assisted UNIT a few times. (DW: The Sontaran Stratagem/The Poison Sky, Planet of the Dead)

As the youngest-appearing incarnation at the time, the Doctor found himself drawing closer to some of his companions than he might have previously, in particular, with Sarah Jane Smith, whom it was later implied, though never stated, may have fallen in love with him. (DW: School Reunion) If any of his other female companions felt the same way, the Doctor, through intent or quirk of personality, did not appear to notice. He tended not to display such feelings himself, not even when accompanied by the often scantily clad Leela, although during one adventure he acknowledged the fact that Romana was attractive. (DW: The Pirate Planet) He was more likely to make remarks such as telling Countess Scarlioni, "You're a beautiful woman ... probably". (DW: City of Death)

Habits and Quirks
Souvenirs from many different worlds littered the fourth incarnation's 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 jelly babies with him, and offer them as a greeting. While past and future incarnations also showed occasional fondness for the sweet, it was never as frequent as this incarnation's love for them. In his later life he developed a great fondness for tinkering about in his 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)

Another habit he had was giving a K9 robot to his departing female companions. When Sarah Jane left, he gave her K9 Mark III. (KAC: A Girl's Best Friend) When Leela stayed on Gallifrey, he gave her K9 Mark I. Lastly, he gave Romana K9 Mark II when she decided to stay in E-Space. (DW: Warriors' Gate)

Appearance
In stark contrast to the elegant and refined, but somewhat flamboyant, figure of his third incarnation, the fourth incarnation was an unkempt, awkward-looking figure, dressed in battered clothing and a ridiculously long, multi-coloured scarf, which had originally been knitted for him by Madame Nostradamus. (DW: The Ark in Space) His dark curly hair was often partially hidden by a large floppy hat. Professor Marius remarked that the Doctor looked like a "space vagrant". (DW: The Invisible Enemy) The fourth incarnation was also notable for being the first incarnation to wear clothing with question mark motifs. The same would later be true of his fifth, sixth and seventh incarnations. (DW: The Leisure Hive, Castrovalva, The Twin Dilemma, Time and the Rani, et al.)

His costume changed throughout his life. His initial costume consisted of a red-brown blazer with elbow patches, baggy grey tweed trousers, a dark brown cardigan with diamond shapes adorning the front, a white dress shirt and a long green neck-tie. (DW: Robot - Revenge of the Cybermen) It changed slightly with a different scarf and hat (DW: Terror of the Zygons) and again with the original scarf, albeit a different waistcoat, shirt and cravat (DW: Planet of Evil). Eventually, the basic style stabilised with a frock coat and some form of a cravat or tie with the above mentioned articles of clothing. (DW: The Android Invasion) He wore several frock coats of different colours, including a dark brown one, (DW: Pyramids of Mars) a light grey one (DW: The Brain of Morbius), and a light brown one.

Throughout his life, his costume alternated with different shirts, cravats, frock coats, waistcoats and other various pieces of clothing until he later settled on one outfit consisting of an open-neck shirt, an unbuttoned waistcoat, a tan frock coat, knee-high leather boots, trousers and of course the famous scarf. (DW: The Power of Kroll) He wore this costume alternating between ankle-high leather shoes and the boots. (DW: City of Death, et al.) From his second attempt to reach Brighton Pavilion, however, his costume changed dramatically, with a red and maroon colour scheme. This consisted of a full-length maroon coat, waistcoat, trousers, buccaneer-style leather boots, a Poet's Hat, a white open-neck dress shirt with question marks adorning the collars (a trait that would continue through to his fifth, sixth and seventh incarnations) and a new scarf. (DW: The Leisure Hive) This scarf was longer than his previous scarves; when it was looped around his neck, the loop reached the floor, and so did the ends. He adopted a maroon, red and purple colour scheme to match the rest of his clothes. He would continue to wear this until the end of his life. (DW: Logopolis) His costume regenerated slightly when he did, as seen by the Fifth Doctor's ankle-high golf shoes and pulled-up socks instead of the leather boots. (DW: Castrovalva) The Doctor had kept parts of his costume throughout the years. (DW: Time and the Rani, The Christmas Invasion)

Like several of his later incarnations, his pockets were dimensionally transcendental. The array of items he carried included:
 * A seemingly endless supply of Jelly babies.
 * A galactic passport. (DW: Robot)
 * A cricket ball. (DW: The Ark in Space, The Hand of Fear)
 * A yo-yo, which, with a sheepish grin, he would explain was useful for taking gravity readings. (DW: The Ark in Space)
 * A selection of books, including his 500 Year Diary, (DW: The Sontaran Experiment) Oolon Caluphid's Origins of the Universe and a Tibetan language handbook. (DW: The Creature from the Pit)
 * A magnifying glass, gemstones, handcuffs, and an etheric beam locator which also detects ion-charged emissions. (DW: Genesis of the Daleks)
 * A picklock. (DW: Pyramids of Mars).
 * A football rattle.
 * A magician's cane. (DW: The Hand of Fear)
 * A clockwork egg-timer. (DW: The Face of Evil)
 * A breathing tube, a barrister's wig, and an instant camera. (DW: City of Death).
 * On one occasion, he even dropped a cup containing a hot beverage into his pocket. (DW: The Power of Kroll)

Casting
Actors considered for the role of the fourth incarnation included Michael Bentine, Bernard Cribbins, Graham Crowden, Fulton Mackay and Jim Dale. Tom Baker was cast based on his role as the villain Koura in The Golden Voyage of Sinbad.

Appearance
According to the creators of the show and Baker, the character's look was originally based on paintings and posters by Henri de Toulouse-Lautrec of his friend, Aristide Bruant, a singer and nightclub owner whose trademark was a black cloak and long red scarf.

Possible romances
Since the fourth incarnation was the youngest in appearance at the time, he therefore appeared closer in age to his companions. This led to concerns being expressed of possible "hanky panky in the TARDIS", a term often used in the tabloid press to suggest the impression of off-screen dalliances between the various Doctors and their young, female companions.

Perhaps to address this, according to the Information Text commentary on the 2007 DVD release of The Stones of Blood, Baker generally tried to emphasise the asexuality of the character, apart from possible subtle romantic tension such as that with Sarah Jane Smith. Despite this, Baker was not above tossing in occasional visual jokes that suggested sexual tension. For example, in The Stones of Blood the Doctor and Romana have to huddle close in order to be within the confines of a transporter beam and enter what would, in normal circumstances, be seen as a romantic clinch, but neither character appears to recognise this. Likewise, the Doctor and Romana are forced into close proximity in The Ribos Operation when hiding from Graff Vynda-K and neither seem to recognise this as a romantic moment.

In popular culture
The fourth incarnation's distinctive appearance and mannerisms have made him a target for affectionate parody. The character appeared several times on The Simpsons and twice on Robot Chicken. Even in 2011, a full 30 years after he left his tenure as the Doctor, an animated parody of his incarnation appeared an episode of Futurama "Mobius Dick". In "Hugo 2: Whodunnit?", a computer game, the player's character can save Tom Baker's Doctor from a Dalek, who in return he gives the player his infamous sonic screwdriver.

He is frequently impersonated by impressionist Jon Culshaw on the radio and television series Dead Ringers. Even Barney Miller had an episode featuring an eccentric man claiming to be a time-traveller, and wearing a long striped scarf. Archival footage of the fourth incarnation's first title sequence was also used in the Family Guy episode "Blue Harvest" to represent and parody Star Wars's hyperspace.

Tom Baker, as the narrator of the series Little Britain, has referenced Doctor Who. He also appeared in Doctor Who and the Daleks in The Seven Keys to Doomsday, a stage play that opened two weeks before Baker began his tenure as the Doctor. In the play, Trevor Martin plays an alternative version of the fourth incarnation.

In the book Return of the Bunny Suicides, there is a scene in which a bunny sits on top of the TARDIS with a noose around its neck as the fourth incarnation runs into it, being chased by a Dalek.

Peter Jackson wore a costume similar to the fourth incarnation's when he played Derek in his film Bad Taste.

On The Big Bang Theory, in the episode, "The Justice League Recombination", Stuart wears the Fourth Doctor's costume to a New Year's Eve costume party at his comic book shop.

Reprising the role
Unlike his predecessor Jon Pertwee and his successors Peter Davison, Colin Baker, Sylvester McCoy and Paul McGann, Tom Baker was notoriously hesitant to reprise the role of the Doctor. Originally intended as a major player in the 20th-anniversary special, DW: The Five Doctors, Baker pulled out before production began, citing other obligations as his reasoning. The production team rewrote the scripts to give much of his role to the Fifth Doctor, and included the Fourth Doctor by making use of unbroadcast footage from DW: Shada. A Madame Tussauds wax mannequin of his incarnation was used in publicity shots to keep the "five Doctors" concept afloat.

In 1993, Baker agreed to reprise the role for the opening scenes of the charity special DW: Dimensions in Time, but the fourth incarnation did not otherwise interact with any of the other incarnations or companions in the piece. Baker had also considered playing the Doctor again for a 30th anniversary special, The Dark Dimension, which was cancelled before filming began. Around this time, he also introduced a VHS reconstruction of Shada, though not apparently in character as the Doctor.

Despite his hesitancy to play the role again, Baker made frequent appearances on DVD releases of his stories, recording audio commentaries for many and conducting on-camera interviews for others.

In the 2000s, Baker made a tentative step towards reprising the role by agreeing to record audio books for BBC Audio, reading the texts from several Target novelisations from his era. Finally, in 2009, Baker agreed to return to the role of the Doctor in a dramatic context, performing the five-part BBCR: Hornets' Nest story arc, again for BBC Audio, in which he was paired up with Richard Franklin, reprising the Pertwee-era companion Mike Yates.

In March 2010, Baker announced on his official website that he was in discussions with Big Finish Productions to record Doctor Who audio dramas for the company. . Big Finish confirmed this on 3rd June 2010. A few days later it was also confirmed that Baker would be doing additional stories for BBC Audio, BBCR: Demon Quest, released at end of 2010.