The Eleventh Doctor is whimsical and energetic, but also brooding and manipulative. His number one rule for his Companions is that the Doctor always lies, which takes the sneakiness and deceitfulness the Seventh Doctor to another level. Though he initially feels out of place with humans, not understanding basic elements of social interactions, the Eleventh Doctor eventually becomes downright domestic (in his way) with River and, after his relationship with her progresses and she heads to the Library, he becomes quite leery in his interactions with his female allies and Companions. He’s impatient and easily bored, struggling to sit still at any given moment while valuing stability for his Companions in a way he hasn’t previously and traveling with Companions who have (comparatively) normal home lives separate from their multiple-story adventures with him.
The War Doctor is cagey and a little cranky. He is tired after what appears to have been a long, long life of trying to resolve the Time War. Though he is battle-scarred, he still feels very young when compared to his successors, the Ninth, Tenth, and Eleventh Doctors. When he meets them, he finds the Tenth and Eleventh to be annoyingly immature and mannered. He also has a strong sense of duty and feels an obligation to end the Time War, no matter the cost to himself.
The Eighth Doctor is romantic and easy going, one of the most human of his incarnations and certainly an ardent admirer and appreciator of humanity. He finds wonder and joy in the smallest of things and has an undeniable enthusiasm for life, though he’s far more relaxed than his more frenetic and bouncy Tenth and Eleventh counterparts. He has a pleasant demeanor and friendly wit and, despite the horrors he’s seen in the Time War, he tries his best to keep a twinkle in his eye and smile on his face. He’s also tends towards being formal and dignified in his interactions with his Companions and seems very much a proper British gentleman, though without the restraint or detachment that might accompany this.
The Fifth Doctor is the first Doctor to feel every bit his age, which is of course contrasted by his physical appearance (Peter Davison was 29 when he took on the role, making him the youngest actor to play the Doctor until Matt Smith, who was 26 when he was cast). He’s thoughtful and still, far less wordy than his predecessor, and perhaps partially due to the youth of his Companions, the Fifth Doctor is the most paternal since the First Doctor. He can be stern, one of the earliest to show the Fury of a Time Lord so common to the modern series, but he also has a sense of fun, taking time off here and there to catch a game of cricket and relax. He’s also the most approachable of the Classic Doctors, with a breezy demeanor that contrasts the Fourth Doctor’s manic energy.
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.
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.
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.
The Seventh Doctor begins his tenure as a rather comical, light-hearted figure. Sylvester McCoy was known for his vaudeville-style clowning and humor and the early Seventh Doctor stories play into this. As his stories progress, however, he becomes a much darker, more still figure and he’s perhaps the most manipulative and deceptive of the Doctors. He has an incredibly close bond with Ace, who is very much his protégé and a daughter figure, and this relationship is a clear precursor to the more intense, more closely-examined Doctor/Companion relationships to come in NuWho (minus the romance). It’s highly implied during this time that the Doctor has a far more significant, secret past than his “Time Lord on the run” cover story, but this is quickly backed away from later. This ominous, looming secrecy gives the Seventh Doctor an air of foreboding and drama that counterbalances his early and occasional silliness quite well.
The Fourth Doctor can perhaps best be described as alien. After the very human Third Doctor and UNIT era, this new wide-eyed and unpredictable Doctor is a dramatic change and while each Doctor to this point is brilliant and clearly the smartest man in whatever room he enters, this incarnation is the first to embody that brand of genius that can keep any number of seemingly random threads whirling in their brain at a given moment, jumping between them at will and only later revealing to the rest of the room how they’re connected. He has a manic energy and bluster that seems endless as well as a penchant for bickering with or teasing his Companions, particularly Sarah Jane and Romana I and though he can be deadly serious, this Doctor is most likely to be found with a wide grin on his face and mad schemes percolating behind his eyes.
The Sixth Doctor is extremely brash and outgoing. He’s quick to anger, but can calm quickly as well, if he puts his mind to it. He’s incredibly arrogant and self-assured and immediately assumes a position of authority upon encountering a situation that requires his attention. He is blustery and is often short with his Companions, making him among the most difficult Doctors for many fans to embrace. He suffered an extreme reaction to his regeneration and went temporarily mad, lashing out at and attacking his then Companion, Peri. He’s not particularly aware of others’ needs and dispositions, as his mind is usually elsewhere, but he cares deeply for his Companions and, like every Doctor, is incredibly protective of them.
The Ninth Doctor is a tricky one. He often seems carefree and goofy, but this masks deep pain and rage. He’s fresh from the Time War and when confronted with a Dalek, his façade crumbles and he becomes unrecognizable to his Companion, Rose. The Ninth Doctor hates guns (except when faced with the Daleks) and has a slightly contentious, if light-hearted relationship with gunslinger Captain Jack. He always makes sure to give his adversaries the opportunity to leave peacefully, offering to help them find a non-violent solution to their needs (resources, space, etc.) and his joy at finding non-violent solutions is palpable. Like some of his predecessors, most notably the Fifth Doctor, the Ninth Doctor is somewhat taciturn, very still, and extremely thoughtful.