Not much is known about the Doctor's arrival on Earth, what is known, however, is that he was most probably in exile from Time Lords on his home planet of Gallifrey, which he fled stealing a type 40 TARDIS to travel space and through time. The Doctor arrived in London, England in 1963 with his granddaughter, Susan Foreman. On the basis of finding missing parts of the TARDIS, the Doctor and Susan were forced to stay in 1963 England for approximately 5 months. Secretly, however, the Doctor was finding a place to hide the Hand Of Omega. Barbara Wright and Ian Chesterton, two of Susan's schoolteacher's followed her back to the TARDIS one night after noticing her expanded knowledge of Science, even though she couldn't count local currency correctly. Entering the TARDIS, the pair realised its size difference and suspected something alien. Panicking and not knowing how to react, the Doctor kidnapped them and travelled to the year 100,000 BC(also the name of the second episode).
The Second Doctor came around when the First Doctor had to regenerate when his body was dying, partly due to age but mostly due to the fending off of the Cybermen he had just accomplished. However, Ben Jackson(companion) thought him to be someone impersonating the Doctor and handed him over to the Daleks. After escaping from them once more, Polly and Ben had once again learned to trust him. This incarnation dressed similarly to the First Doctor, though he disposed of the blue ring, wore a bow tie and his trousers were sizes too large for him. Childish and loveable, this incarnation was a massive change from his predecessor, but once more possessed huge levels of intelligence. The Second Doctor was also rather cruel and vicious, many times killing his enemies or leaving them in fatal situations, actions which would deeply agitate his companions. A notable skill of the Second Doctor's was his persuasion. He used this many times to get himself out of potentially lethal situations and to help others do the same. Strangely enough, he could also play the recorder, which he played whilst under stress. This Doctor also introduced the Sonic Screwdriver to the series.
After the Second Doctor was forced to regenerate by the Time Lords, the Third Doctor was "born". The Time Lords also jailed him in 20th century Earth, removing his power over the TARDIS. The Doctor then proceeded to join UNIT as a Scientific Advisory so that he could use their facilities to attempt to escape. However, when The Master arrived on Earth, the Time Lords allowed him limited use of the TARDIS and eventually complete freedom after he defeated Omega.
A curly brown haired incarnation, the Fourth Doctor also wore ragged and tattered clothing, which made him sometimes comparable to a tramp. One of the most notable incarnations, mainly due to his knitted scarf(which runs the length to the floor) which was knitted for him by Madame Nostradamus, he also plays the joker oftenly, much like the Second Doctor. He was an excellent judge of character, instantly being able to guess if he could or could not trust said person. The Doctor's great level of intellect was not always clear in this incarnation, but was obviously in existence all the same. He enjoyed ginger beer and jelly babies(which he usually offered out to people) and often carried many items from different planets(a yo-yo seemed to be a favourite toy).
For an unknown reason, when the Fourth Doctor regenerated into his fifth incarnation, many problems occured. The Doctor was dropping into bouts of silence randomly which troubled Tegan and Nyssa, who were attempting to revive him from this. On top of sinking into periods when he feared almost everything, the Doctor also began to mimick and possess previous incarnations' personalities. Finally, the Doctor entered the Zero Room on the TARDIS to recover whilst Nyssa and Tegan guided the TARDIS to Castrovalva, a location where he could regain his healthy status.
In the ending moments of regeneration, the previous incarnation had stated that "this regeneration feels different". The Sixth Doctor, when regenerated, then went delusional, often acting insane and even attempting to strangle his own companion, Peri Brown! After deciding to hide out on Titan III to cool down and settle into his new form, he met a fellow Time Lord, Azmael. With his help, he managed to prevent a crisis on the planet, but the Doctor was still acting insane at times.
Wearing a long, grey overcoat and a beige hat, the Doctor also wore cross stitched clothing, such as scarves. A much more sinister character, the Seventh Doctor would often mention his love of Chess, and how he would play others around like pieces on a Chess board. Although remembered for his sinister personality, he was also a man of many words, often using his speech to escape situations.
The Seventh Doctor regenerated into his eighth incarnation after being accidentally shot by a gang member when his TARDIS materialised in the middle of a shootout. The reason his TARDIS materialised is The Master's doing, after sabotaging the Doctor's ship when travelling. The Doctor, being operated on in a hospital, officially "dies" and is put in the hospital morgue. However, he regenerates and emerges from the morgue and eventually returns to his TARDIS. He also suffered Amnesia after his regeneration.
The Ninth incarnation of the Doctor had short, cropped hair and wore dark clothing with a black leather jacket. This Doctor, like many others before him had the "split personality" of being a calm, reserved person or a frantic, maniac like person, often proclaiming himself brilliant when he had thought of a breakthrough. The battered image of a veteran of war was ubiquitous however and the Doctor showed this often by cursing. The Doctor also spoke with a Northern accent, when questioned on this he replied "Lots of planets have a North". As time progressed, his attitude towards the rest of the universe changed and he often revered other species' lifestyles.
The Tenth Doctor has a cheeky, cheerful personality but still has the curious, serious side of all Doctors aswell. He, like all Doctors is very intelligent. He states in Fear Her that he isn't too keen on cats. He also seems to lack drawing abilities, though as John Smith he seemed to be able to draw Joan Redfern and other aliens he'd seen in his dreams with remarkable accuracy. The Doctor is seen on occasion as a bundle of enthusiasm - exclaiming to scared passengers on the Crusader 50 bus that it was brilliant a new species may have came on board, despite killing 2 people. (Midnight).
Smith was revealed as the Doctor in a special episode of Doctor Who Confidential on Saturday, 3rd January. The 11th Doctor was hotly tipped to be either Chiwetel Ejiofor or Paterson Joseph (who starred as Rodrick in Bad Wolf). Matt was an unknown until the night before he was revealed, when someone placed a large bet on him, drawing attention to his casting.