We first encounter Vicki as a survivor of a spaceship crash on the planet Dido. The Doctor, still reeling from the departure of his granddaughter Susan, rescues Vicki and invites her to travel with him. Vicki becomes like a new granddaughter to The Doctor and the two develop a very close relationship. Coming from the future, Vicki eventually falls in love on Earth in the past and decides to remain there.
Romana is a Time Lady first assigned to travel with the Doctor by the White Guardian* (*Spoilers!). After traveling with him for the Key to Time season, she chooses to regenerate, with fans distinguishing between these incarnations by calling her Romana I or Romana II. Just like the Doctor, she has a distinctly different personality in her new regeneration and she and the Doctor have a distinctly different rapport.
Rory is a nurse from Leadworth who has grown up hearing stories of the Doctor from his friend Amy. Assuming him to be an imaginary figure, he is thrown for a bit of a loop when he meets the Doctor in “The Eleventh Hour”.
Ben is a Cockney sailor set to ship out with the Royal Navy when he meets Polly and, later that night, the Doctor at a club. Ben is a contemporary young man, designed to pair with Polly and follow on from Ian and Steven as the Male Action Hero of the series, given the First Doctor’s advanced age and failing health.
The Third Doctor is very scientifically minded, preferring to tinker in his lab rather than interact with his colleagues at UNIT. He’s a far more action-oriented Doctor than his predecessors, filling the Male Action Hero role himself for the first time. The Third Doctor is somewhat of a dandy, very carefully selecting his outfit and hotwiring a classic car, Bessie, that catches his eye. He can be abrupt with his Companions, but over time he develops strong bonds with them, missing them when they’re gone even coming across as a bit jealous when Jo leaves to get married. The Doctor is rather proud and his inability to operate the TARDIS is a particular sore point (the Time Lords blocked off this knowledge in his brain as a punishment for the initial conflict that caused him to leave Gallifrey). He has a contentious rapport with the Brigadier, as the Brig represents UNIT’s interests, which don’t always coincide with his own, but eventually the two develop a close friendship, with the Brigadier returning (somewhat) frequently over the course of the series to have adventures with almost all of the Doctors.
Jenny is a Victorian-era maid who is involved with Madame Vastra when we first encounter her. They eventually are married and begin functioning as detectives in London, providing the inspiration for Sherlock Holmes and Watson, along with fellow Eleventh Doctor ally Strax, their butler.
Perpugilliam Brown is an American college student on holiday with her stepfather when she nearly drowns and is saved by Turlough. Having been rescued and taken into the TARDIS to recover, Peri is aboard when it takes off, whisking her away with the Doctor, Turlough, and Kamelion to face off with the Master. Peri is studying botany in school, which comes in handy during her travels with the Doctor, and her parents are archeologists, giving her a solid background in that subject as well.
The TARDIS (so named by Susan as an anagram of Time And Relative Dimensions In Space) is a Type 40 time travel capsule stolen from Gallifrey by the First Doctor when he decided to head out with Susan to explore the universe (or ran away, depending on who you ask and when). Though magnificent to the audience’s eyes, and the Doctor’s, most Time Lords consider Type 40s to be rather ramshackle, far from the most advanced or desirable model. It has a history of breaking down to varying degrees. Its chameleon circuit for example, which instantly disguises it to match its surroundings, has been set on ‘60s London for most of the show’s run, though it’s implied both the Doctor and the TARDIS itself are rather fond of this setting and would choose it regardless. Much like the Doctor, the TARDIS seems to regenerate at various points, taking on new control room designs, both based on the Doctor’s preferences and perhaps its own as well.
Katarina is a servant girl from Troy who is tasked with spying on Vicki when the Doctor and his Companions wind up there during the Trojan War. She befriends Vicki and ends up caring for the injured Steven, helping the Doctor carry him into the TARDIS, which convinces her the Doctor is Zeus. At the end of her first story, Katarina joins the Doctor and Steven aboard the TARDIS, though it will not be for long.
Throughout the run of Doctor Who, everyone’s favorite Gallifreyan has encountered many characters and left them, never to be seen again. Others, a select few, he has invited to travel the universe with him, adding an extra dimension to his adventures. There have been some individuals, however, with whom The Doctor has clearly shared a good …
Rose is a seemingly normal teenager working in a shop when she runs into the Doctor. She later proves herself as a Companion and the Doctor clearly sees something in her from the start, but to the untrained eye, she is a rather unremarkable young woman.
Dr. Harry Sullivan is a surgeon working for UNIT when he’s called in to check on the Third Doctor after his fatal dose of radiation at the end of Planet of the Spiders. He arrives just after the Doctor regenerates and is tasked by the Brig to give the Fourth Doctor a physical, leading to one of the most entertaining opening scenes with a new Doctor in the series’ run. Afterward the events of Robot, Harry is swept away in the TARDIS for the Doctor’s next adventure, one TARDIS trip that lasts the next five stories.
The Tenth Doctor is one of the more human Doctors. He’s warm, funny, and rather emotional. He can be incredibly short-sighted and dense when it comes to his Companions’ feelings, but he for the most part is highly emotionally intuitive. Still recovering from the Time War, a wrathful anger lurks beneath his friendly façade, but it very rarely comes out. This Doctor is very energetic, finding it difficult to sit still under normal circumstances, and he talks a mile a minute, a distinct contrast from the Ninth Doctor.
Sara Kingdom is the dedicated, powerful, top agent for the Space Security Service, working under the traitorous Gaurdian of the Solar System Mavic Chen, when she meets the Doctor. Initially an antagonist, Sara discovers Chen’s treachery and switches allegiances, working with the Doctor to bring down him and his allies, the Daleks.
Victoria is a teenager living with her father in England when she becomes embroiled in his dealings with the Daleks and, later, the Doctor. After her father’s death, she joins the Doctor and Jamie on the TARDIS, having nowhere else to go. She is a girl of her time, making her at times rather unsuited to life on the TARDIS.
Wilfred Mott is a pensioner and an amateur astronomer whose love of the stars has rubbed off on his adventurous granddaughter, Donna Noble. Wilf is a veteran, having served in WWII, though without killing anyone, and he is able to relate to the Doctor as a fellow former soldier.
Tegan is an Australian on her way to Heathrow to start her job as a stewardess for Air Australia when her aunt’s car gets a flat tire and she enters the TARDIS thinking it’s a police box, intending to call for help. While she’s wandering through the TARDIS, the Master kills her aunt, causing her to be swept into the Doctor’s struggle against him.
The Second Doctor is wily, silly, and thoughtful. He’s happy to play the clown or sit quietly in the background, allowing others to underestimate him. He has no interest in recognition or praise, often slipping away with his Companions after saving the day as soon as those he’s just helped start trying to celebrate him or rope him into assisting them further. Unlike the First Doctor’s early grouchiness and avuncular grandfather persona, the Second Doctor is more of a crazy uncle, less interested in educating or otherwise bettering his Companions and more focused on them as individuals and friends. He opts for disguise and deception over outright confrontation when it comes to gathering information and defeating his foes and the Second Doctor is perhaps best known for his close bond and comedy duo rapport with Jamie, the longest-running Companion in the series.
Amelia Pond is a child when the TARDIS crash lands in her back yard. When the Doctor attempts to hop the TARDIS forward 5 minutes and overshoots by twelve years, Amy grows up with the Doctor as her childhood imaginary friend. She has somewhat of a difficult childhood, acting out and insisting that the Doctor is real to the point where she’s put into therapy. Amy is incredibly close with her best friend Mels and becomes good friends with Rory as well, and the two eventually start dating. Amy is working as a kissogram and still living in the same house when she next encounters the Doctor as a late teenager.
Steven is a human from the 23rd century who has been stranded on the planet Mechanus for two years when the Doctor, Ian, Barbara, and Vicki stumble across him while fleeing the Daleks and the Mechanoids. Rather than being invited aboard the TARDIS, Steven stows away, but he quickly becomes part of the TARDIS team, picking up the slack for the just-departed Ian in the Male Action Hero role.
Harriet Jones is a public servant representing Flydale North at 10 Downing Street when she becomes swept up in the Doctor and Rose’s attempts to stop the Slitheen. When we later encounter her, she’s risen to Prime Minister and though she’s driven out of office, she continues her work defending the Earth from her home.
Mel is a computer genius from the near future (when her stories aired, that is. She’s from the early 21st century). As the Doctor, and the audience, first meet her after she’s already met him, we don’t find out much about her backstory or her family and friends.
Christina is a lower-level aristocrat who moonlights as a notorious art thief. She is on the run from her latest heist, being pursued by the police, when she encounters the Doctor on the bus and sets off on their adventure.