The Ninth Doctor (Christopher Eccleston) regenerates into the Tenth Doctor (David Tennant) at the climax of the 2005 series finale, "The Parting of the Ways"; he re-introduces himself to his companion Rose Tyler (Billie Piper) in an untitled Children in Need mini-episode. In the Christmas special, he is in a comatose state for most of the episode, following his regeneration. After eventually waking up, he defeats the alien Sycorax and saves Earth; in the process, he loses a hand, which regrows owing to his recent regeneration. Amongst other 2006 series adventures, the Doctor and Rose save Queen Victoria (Pauline Collins) from a werewolf, resulting in the creation of the anti-alien Torchwood Institute. The Doctor shares an adventure with two former companions, journalist Sarah Jane Smith (Elisabeth Sladen) and robot dog K-9 (John Leeson), before taking on Rose's boyfriend Mickey (Noel Clarke) as a second companion. The series finale takes place in contemporary London, where modern-day Torchwood is the scene for war between the evil alien Daleks and parallel-universe cyborgs the Cybermen; saving the Earth costs the Doctor Rose, who is stranded in a parallel universe, along with Mickey and her mother, in "Doomsday".
In the closing scene of "Doomsday", a mysterious bride (Catherine Tate) inexplicably appears in his TARDIS. The 2006 Christmas special sees the Doctor and bride-to-be Donna Noble save the Earth; Donna saves the Doctor from going too far in his revenge against the alien Racnoss and declines his offer of companionship. In the 2007 series, the Doctor takes on Martha Jones (Freema Agyeman) as his new companion. Together, they witness the mysterious Face of Boe (Struan Rodger) prophesy to the Doctor that "you are not alone." They are rejoined by former companion Captain Jack Harkness (John Barrowman) in a three-episode adventure where presumed-deceased archenemy and fellow Time Lord the Master (John Simm) becomes Prime Minister of the United Kingdom and enslaves the Doctor for one year. Martha's plan sees the Doctor infused with the world's psychic energies, and he easily defeats the Master, who seemingly refuses to regenerate and dies in the Doctor's arms. Following this adventure, in the dénouement of series finale "Last of the Time Lords", Jack and Martha both depart the TARDIS, and the Doctor is shocked to see what appears to be the RMS Titanic crash into it. Set moments prior, another Children in Need mini-episode, "Time Crash", features a brief encounter between Tennant's Tenth Doctor and theFifth Doctor (Peter Davison), containing meta-humour surrounding Davison's Doctor having been a young David Tennant's favourite. In parallel with the third series, Tennant lends his voice to the animated serial The Infinite Quest.
The 2007 Christmas special sees the Doctor and a waitress, Astrid (Kylie Minogue), save the Earth from the impending crash of the starship Titanic; Astrid dies heroically, and the Doctor encounters Wilfred Mott (Bernard Cribbins) for the first time. In the 2008 series première episode, the Doctor is reunited with Donna Noble, Mott's granddaughter, who becomes his regular companion. In "Planet of the Ood", the alien Ood prophesy the Tenth Doctor's demise. Martha accompanies them for three episodes; in two, the Doctor battles the alien Sontarans, and last of which sees him become a father of sorts to Jenny (Georgia Moffett), in "The Doctor's Daughter". He meets archaeologist and future companion River Song (Alex Kingston) for the first time from his perspective in the two-parter "Silence in the Library"/"Forest of the Dead"; she dies, but he stores her consciousness to a hard drive to live on forever, after accepting that one day she will come to mean a lot to him. After Donna encounters Rose in an alternate timeline in "Turn Left", the Doctor realises that it must herald the end of the world. In finale episodes "The Stolen Earth" and "Journey's End" (which cross over with spin-offs Torchwood and The Sarah Jane Adventures), the Doctor and Donna reunite with former companions Rose, Sarah Jane, Martha, Jack, and Mickey to save the universe from Davros (Julian Bleach), the creator of the Daleks. A half-human Doctor is created from the Doctor's previously severed hand, and Donna is given the mind of a Time Lord; the Human Doctor enjoys a happy ending with Rose in the parallel universe, though the Doctor is forced to erase Donna's memories to save her life, leaving him alone. A Doctor Who Prom mini-episode, "Music of the Spheres", features a lone Doctor composing his musical Ode to the Universe before being interrupted by the small alien Graske (Jimmy Vee).
In lieu of a 2009 series, Tennant appears as the Tenth Doctor, without a regular companion, in several special episodes over the course of 2008 and 2009, the last of which aired on New Year's Day, 2010. In the Christmas special "The Next Doctor", the Doctor mistakenly believes he has met a later incarnation of himself in an amnesiac Londoner (David Morrissey), with whom he saves Victorian-era London. "Planet of the Dead" (Easter 2009) features jewel thief Lady Christina de Souza(Michelle Ryan) as the Doctor's one-off companion, and the Doctor is presented with a prophecy of his imminent death. Tennant makes a crossover appearance in a The Sarah Jane Adventures two-parter, The Wedding of Sarah Jane Smith, in which a powerful being known as the Trickster (Paul Marc Davis) also alludes to the Tenth Doctor's impending demise. In "The Waters of Mars", the Doctor tries to alter history and avert the death of one-off companion Adelaide Brooke (Lindsay Duncan); when she commits suicide, he begins to feel his mortality weigh down upon him. In the animated serial Dreamland, the Doctor is joined by two one-off companions in 1950sRoswell, New Mexico. In the two-part send-off The End of Time, the Doctor confronts the Ood about their original prophecy and is led to contemporary Earth where, in the second part, the again-resurrected Master (Simm) restores Gallifrey and the Time Lords to existence, although he redeems himself by assisting the Doctor to defeat Time Lord President Rassilon (Timothy Dalton) before disappearing alongside the other Time Lords. The Doctor sacrifices his life to save Wilfred Mott, exposing himself to 500,000 rads of deadly radiation and triggering his regeneration. He holds it back and is shown visiting several companions.[a] He gives Donna a winning lottery ticket on her wedding day, buying it with money he borrowed from her late father in the past, saves Martha and Mickey from a Sontaran sniper, saves Sarah Jane's son Luke(Tommy Knight) from a car, introduces Jack to a romantic interest (Russell Tovey), and finally, just before regenerating into the Eleventh Doctor (Matt Smith), he informs Rose in 2005 that she is about to have a "great year". As he begins regenerating once in the TARDIS, his last words are "I don't want to go".
Tennant reprises the role for the show's 50th anniversary in "The Day of the Doctor" (2013), appearing alongside the Eleventh Doctor (Smith) and a forgotten past incarnation played by John Hurt. In the special, in which we view scenes from the Tenth Doctor's time taking place between Waters of Mars and The End of Time, the Doctor unintentionally marries Queen Elizabeth I (Joanna Page) while luring out a Zygon before leaving her at the altar, causing her to develop a grudge against him. While he helped the other Doctors in saving Gallifrey at the Time War's conclusion, he does not retain memories of the event.
The Tenth Doctor generally displays a light-hearted, talkative, easy-going, witty, and cheeky manner, but repeatedly demonstrates a vengeful and unforgiving streak as well. This emerged early on when he sends the Sycorax leader (who is attacking him from behind) falling to his death while commenting that, with him, there are "no second chances". In "School Reunion", he acknowledges that he is less merciful than he used to be and has stuck to his "one warning" code, punishing his enemies if they persist in their hostilities. This is demonstrated in "The Runaway Bride" when he drowns the Empress ofRacnoss' children and stoically watches on, prompting Donna Noble to declare that he needs somebody to stop him, and in "The Family of Blood" where he gives each Family member an individual and eternal punishment. His strong personal sense of justice makes him quick to anger when he feels it is violated, as in "New Earth" when he learns of the plague farm run by the Sisters of Plenitude, he brings down their entire operation. When Prime Minister Harriet Jonesgives an order to destroy the retreating Sycorax ship against his intentions, he brings down her government in six words, "Don't you think she looks tired?", which reaches the press via her assistant's headset. In "The Waters of Mars", he goes so far as to declare himself above the laws of time, although there are catastrophic consequences as a result.
This is coupled, however, with an intense sense of regret of the deaths of both his friends and enemies. In "Journey's End", he has a flashback of those who have died instead of/for him, including Astrid Peth, Jenny, Luke Rattigan, Lynda Moss, and the hostess from "Midnight". He also offers Davros the chance to escape the destruction of the Dalek mothership, but Davros spits the chance back at him, calling him the "Destroyer of Worlds". A recurring line on the part of the Tenth Doctor is his saying that he is "so sorry" for actions he takes, even as he takes them. The loss of his companions and people he befriended becomes a sensitive issue and a mere mention may trigger a sudden outburst of anger without warning. In "The Doctor's Daughter" he explains to his daughter Jenny how "killing...infects [you] and once it does you'll never get rid of it" and that the worst part of it was that he "became clever", reflecting on his involvement in the Time War and witnessing the destruction of his own kind, friends and enemies.
The Tenth Doctor has a tendency to babble, mixing apparent nonsense with vital information, sometimes acting erratically to put his enemies off-guard. He is prone to making comments that to outsiders seem obtuse or rude, sometimes to his own embarrassment. In "The Christmas Invasion" and "Tooth and Claw", he is surprised at his own unintentional rudeness when making disparaging remarks, and Jack Harkness, after reuniting with the Doctor, notes that his "new regeneration (is) kinda cheeky".He has a tendency to use technobabble to describe scientific concepts before substituting it with a simpler, analogous explanation, such as his description of non-linear temporal physics as "a big ball of wibbly wobbly, timey wimey stuff". He is also able to rapidly switch between moods, from mania to anger to nonchalance and uses this as a form of reverse psychology on several occasions ("Fear Her", "Love & Monsters" and "Army of Ghosts"). In the latter, by switching gears suddenly after failing to dissuade Yvonne Hartman from her current activities, he is able to make her uncertain enough to get his way.
Another recurring theme in the Tenth Doctor's stories is his intense loneliness. In "School Reunion", he describes the ability of Time Lords to live so long as a curse, because while his human companions all someday leave him and eventually die, he continues to live. He also commented to several of his female companions, especially to Rose and Donna, that while they may spend the rest of their lives with him, he is unable to do so due to his ability to regenerate. Other characters have also commented on the Tenth Doctor's loneliness. During a conversation with his nemesis, the Master, he admits that since the end of the Time War and the loss of the other Time Lords, he has been "alone ever since". Indeed, when the Master subsequently dies, the Doctor openly weeps over his body. In "The End of Time", he ultimately ends up regenerating in the TARDIS alone, despite visits to his past companions in his dying hours.
The Tenth Doctor is more extroverted and gregarious than his predecessor, quickly establishing a firmer rapport with Rose Tyler's friends and family than he ever did in his previous incarnation. He is openly fond of mankind and is apparently in awe of their tenacity and curiosity, a trait previously exhibited by his fourth incarnation. In "The Impossible Planet", he hugs the leader of an Earth expedition for daring to explore a planet orbiting a black hole merely "because it was there". In "The Age of Steel", he describes human beings as both brilliant and stupid in the same sentence while arguing the necessity of emotions with the Cyber-Controller. The Doctor even goes so far as to exclaim he's willing to battle the Master across the cosmos so long as he leaves Earth alone in "The Sound of Drums". However, he is also quick to criticise mankind when he feels it is necessary. Indeed, his confidence in the human race becomes far less pronounced in later series, and at the end of "Midnight" he is left speechless after witnessing the steps humans can become willing to take when placed in a threatening situation, as he is almost killed by a panicky group of people who turn on him.
The 2006 series continued the exploration of the Doctor's romantic aspects, with the Tenth Doctor sharing kisses with Rose (albeit while she was possessed by Lady Cassandra) and Madame de Pompadour. In "School Reunion", Sarah Jane Smith all but confesses that she had been in love with him. In "Doomsday", during their farewell, Rose tells the Doctor she loves him; he begins to reply but only manages to say her name before the transmission is cut off, leaving him alone in the TARDIS with tears on his cheeks. After this, whenever he is reminded of Rose he sometimes becomes depressed or pensive. Later, in Series 4, Rose returns for the series finale and ends up with a copy of the Doctor who is human, and thus able to spend his life with her. In Series 3, the Doctor gradually learns that Martha harbours feelings for him before she leaves his company – which he inadvertently inspires by kissing her as a distraction – and also exchanges kisses with Astrid in honour of "an old tradition" from her home planet, but really seems to be an intense connection and like for each other. Following the complications with Martha, for which he blames himself, the Doctor seems reluctant to embark on any other potentially romantic companionship, and makes sure that before allowing her to join him, Donna understands that all he wants is a friend. In keeping with this, when he is poisoned in "The Unicorn and the Wasp" and asks Donna to give him a shock of some kind, kissing him proves to be so out-of-character for her that it is sufficient to trigger the detox process.
The Tenth Doctor sometimes dons a pair of spectacles, like the Fifth Doctor, whose youthful appearance he shares. In the 2007 Children in Need special, "Time Crash", the Tenth Doctor notes other inherited/inspired tendencies when meeting the Fifth Doctor, aside from "the brainy specs" (which he observes were worn by the Fifth simply to look clever rather than out of necessity, therefore implying that his are used for the same reason despite the Fifth Doctor stating twice in series that he was actually near-sighted in his left eye ("Castrovalva") and actually needed a corrective lens for that eye), such as wearing plimsolls (trainers) and both of their voices becoming high-pitched when shouting. He also exhibits a remarkable sense of taste, again similar to the Fifth Doctor ("Planet of Fire"), able to identify the blood type of a blood sample ("The Christmas Invasion") or the presence of mistletoe oil ("Tooth and Claw") just by licking. He also shares the Fifth Doctor's skill with a cricket ball, as demonstrated in "Human Nature". Another parallel that the Tenth Doctor shares with the Fifth Doctor is his semi-close involvement with the Master. This too is mentioned in "Time Crash." The Tenth also admitted to the Fifth that he was the Tenth's favourite past incarnation.
The Tenth Doctor speaks with an Estuary English accent, rather than the Greater Manchester accent (Christopher Eccleston's own accent) that the Ninth Doctor used, theReceived Pronunciation of most earlier Doctors, or Tennant's natural Scottish English. David Tennant told SFX magazine in 2006 that Russell T Davies had asked him to drop his natural Scottish accent, because he felt "we'd like to not go for another obvious regional accent, because I suppose they'd done that". In a 23 December interview on BBC Radio 1, Tennant explained that a line had been scripted for the Christmas special explaining that the newly regenerated Doctor had imprinted on Rose Tyler's accent, "like a chick hatching from an egg", but the line was cut from the final episode. The Tenth Doctor has displayed a flexibility in changing accents, having spoken in an American Appalachian accent in "The Christmas Invasion", and a Highland Scottish accent in "Tooth and Claw" at various times in the episodes.
Like the Ninth Doctor, the Tenth Doctor used his sonic screwdriver quite often. This Doctor relied heavily on the device, and chided his fifth incarnation for going "hands free" in "Time Crash", a reference to the Fifth Doctor's loss of the device in "The Visitation". This reliance came to a head when the screwdriver was burned out in "Smith and Jones", having been pushed past its limits in order to boost the radiation output of an X-ray machine. He obtains another screwdriver by the end of the episode.
Much as the Ninth Doctor frequently declared things "Fantastic!", this Doctor has also favoured certain phrases on various occasions, such as "Brilliant!", "oh yes!" (used in an exuberant fashion, often when he has successfully done something), "I'm sorry, I'm so sorry", and the French command "Allons-y" ("Let's go"). The latter was first used in "Army of Ghosts", where the Doctor stated that he should say it more often and that he would love to meet someone named Alonso so he could say "Allons-y, Alonso!", eventually achieving this aim in "Voyage of the Damned" with midshipman Alonso Frame. He also often used the Italian expression Molto bene ("Very good"). In addition, he often clarifies his own mistakes by beginning with an elongated "Well..." Like his predecessor, the Tenth Doctor shows a fondness for human popular culture—a characteristic not all of his previous incarnations seemed to share—but even more so, to the point where he finds himself unknowingly quoting the song "Circle of Life" from Disney's The Lion King during a confrontation with the Sycorax leader, dropping a reference to Kylie Minogue's Never Too Late, referring to the Harry Potter books twice during an encounter with William Shakespeare, and proclaiming his fighting of the Sycorax leader while wearing pyjamas "very Arthur Dent".