Visibly youthful and tending to leap into dangerous situations with an elated "Geronimo!", the Eleventh Doctor is quizzical and abrupt, fascinated by things that don't belong. He's can become distracted enough not to see a threat to his friends, but commits himself utterly to removing them from danger. He finds beauty in the infinite variability of the universe, and reacts to the sight of something new with a huge grin. He carries an intense guilt for the actions he's taken in the past, and his self-hatred, when released by an alien force, once endangered himself and his companions. Nonetheless he is hugely confident in his own abilities and relishes a challenge. Main companions: Amy, Rory.
David Tennant as the Tenth Doctor
The Tenth Doctor (2006-2009) is boisterous and kinetic,switching easily between glib repartee and fierce denunciation. His ready smile disarms strangers, but his loner nature expresses itself in self-consciousness in social situations, especially those involving his companions' families. His boyish enthusiasm often propels him straight to any crisis (his catch-phrase is "allons-y!"). Though passionate he is able to fall in love only by becoming fully human. His ego finally allows him to think of himself as the Time Lord, altering events as he sees fit, only to tragically learn the cost of his hubris and repent, though he's angry at having to regenerate before he's ready. Main companions: Rose, Mickey, Jack, Martha, Donna.
Christopher Eccleston as the Ninth Doctor
The Ninth Doctor (2005), though impatient with folly, is generally exuberant (discovering a solution or new idea spurs him to shout, "Fantastic!"), but his cheery demeanor often slips to reveal a grimness born of his involvement the Time War, the deadly confrontation between the Time Lords and the Daleks that destroyed both races (which took place before the events shown in the new series). This roughness is in large part assuaged by the presence of Rose Tyler, and in the end he dies to save her from destruction. Companions: Rose, Jack.
Paul McGann as the Eighth Doctor
The Eighth Doctor (1996), like his predecessor, endured a regeneration crisis of extended amnesia, but soon recovered and was able to prevent his arch-nemesis, the Master, from opening the Eye of Harmony and thereby destroying Earth. Unlike other incarnations he displays physical affection toward his companion, and even claims (fatuously) to be half-human. He also agrees with the assessment that he's British. His most prevalent characteristic is to dispense random, specific advice about the future to strangers he encounters. He can ride a motorcycle and gets his way with a truculent policeman by threatening himself with a gun. It is (implicitly) the Eighth Doctor who fights in the Time War, but this has not been shown. Companion: Grace.
Sylvester McCoy as the Seventh Doctor
The Seventh Doctor (1987-1989, 1996) starts out seeming to be something of an elfin jester, but over time he reveals a penchant for complex machinations -- even manipulating his unwitting companions into sometimes painful self-discovery. Secretive, pacifist, and ready to adopt a clownish demeanor for fun or to mislead, in turns jittery and serene, he expresses a responsibility for his friends and for the universe, enjoys playing with words and ideas, and doffs his straw boater in polite greeting. He might distract a guard with a discussion of existentialist philosophy, or advance on a man threatening to shoot him with a direct challenge to the stranger's beliefs, challenging him to be a killer and end the Doctor's life. Companions: Mel, Ace.
Colin Baker as the Sixth Doctor
Larger than life, easily irritated, and dressed in garish clothing, the Sixth Doctor (1984-1986) is far from unassuming and quick to take matters into his own hands if he senses injustice or evil. His brash demeanor sometimes distracts his opponents from his deeper motivations, but while capable of charm he's often confrontational with friends and enemies alike. When sent on a mission by the Time Lords without his knowledge he's resentful but does not hesitate to help those he's sent to save, and rails at the Time Lords when he's taken out of time on his way to prevent a murder. Companions: Peri, Mel.
Peter Davison as the Fifth Doctor
Genial and unfailingly polite, the Fifth Doctor (1982-1984) can range from warm gratitude to icy rage. Physically energetic (even including trainers as part of his dress), he sometimes literally rushes headlong into situations without a fully conceived plan. He wears his deep compassion on his sleeve, willingly risking his life for communities and individuals alike, but is still able to watch the Master seem to die and to destroy, at its request, the mind-controlled android Kamelion. He places his life in the hands of someone he knows has plotted against him, as an act of faith. He ultimately dies to save a single life. Companions: Adric, Nyssa, Tegan, Turlough, Kamelion, Peri.
Tom Baker as the Fourth Doctor
Tall, rangy, with a big mop of curly hair and a toothy grin, the Fourth Doctor (1974-1981) is fun-loving, disarmingly madcap, and prone to cracking jokes even when he's in deadly earnest. A certain detachment allows him to take a long view, laughing at the foibles of the humans he loves and ready to see beyond an immediate tragedy to a larger one looming beyond. He can take umbrage at a slight to his handwriting but admits he doesn't always make sense. He sees himself walking the universe as an agent against evil, and while deeply fond of his companions expresses exasperation at their ability to get in his way, later claiming never to choose who he travels with. Companions: Sarah Jane, Leela, K-9, Romana I, Romana II, Adric, Nyssa, Tegan.
Jon Pertwee as the Third Doctor
Avuncular and patrician, the Third Doctor (1970-1974) partners with authority during a temporary exile on Earth in order to defend humanity from both merciless invaders and their own shortsightedness. Dry, whimsical, and a man of action ready to engage in single combat with his foe, he trusts in his own abilities and is not above enjoying respect and acclaim, though he ultimately comes to recognize his egotism as his greatest flaw. He's quick to express outrage at injustice, the larger the scale, the better, and embarks on epic quests to prevent intergalactic war. Companions: Liz, The Brigadier, Mike, Benton, Jo, Sarah Jane.
Patrick Troughton as the Second Doctor
The Second Doctor (1966-1969) delights in exploration and discovery. Though playful and even clownish at times, he's quite capable of striding into the midst of a crisis and convincing others of his acumen and abilities. He's skeptical of power and willing to tackle mighty institutions to remedy any kind of injustice, and outrage can sometimes get the better of his diplomatic skill. Having rejected and run away from his own people, the Time Lords, he's willing to call upon them when a villainous scheme proves too massive for him to unravel; after undergoing a trial for violating his race's laws against intervention he agrees to undertake clandestine missions for them in exchange for his freedom. Companions: Ben, Polly, Jamie, Victoria, Zoe.
William Hartnell as the First Doctor
Sometimes stern and gruff, at other times breaking into giggles over his own ingenuity, the First Doctor (1963-1966) allows the TARDIS to take him wherever it may, and is quick to investigate whatever he finds there. Though often a spectator in time, saying established history cannot be changed, he actively engages those who seek to manipulate and harm others. He progressively sees himself as the sworn enemy of evil races like the Daleks. He describes himself as "a citizen of the galaxy, and a gentleman to boot!" When his granddaughter finds love, he knows he must leave her, as she would be unwilling to leave him. Companions: Susan, Ian, Barbara, Vicki, Steven, Sara Kingdom, Katarina, Dodo, Ben, Polly.