First Doctor

The First Doctor is the original incarnation of the Doctor. He was originally portrayed by actor William Hartnell, but has since been played by actors Richard Hurndall and David Bradley.

Within the series' narrative, the Doctor is a centuries-old alien Time Lord from the planet Gallifrey who travels in time and space in his TARDIS, frequently with companions. At the end of life, the Doctor can regenerate his body; as a result, his physical appearance and personality change. Hartnell's Doctor is the initial form of the Doctor portrayed in the series. The concept of regeneration, initially referred to as a "renewal," was introduced when Hartnell needed to leave the series, and consequently has extended the life of the show for many years.

His original companions were his granddaughter Susan and her schoolteachers Ian Chesterton and Barbara Wright. In later episodes, he travelled alongside 25th century orphan Vicki, space pilot Steven Taylor, Trojan handmaiden Katarina, the ruthless Sara Kingdom, and sixties flower child Dodo Chaplet. His final on-screen companions were the sailor Ben Jackson and the posh and sophisticated Polly Wright. Of the 134 episodes Hartnell appeared in as a regular, 44 are missing.

Biography
The toll of years put strain on the Doctor's elderly frame. After defeating the Cybermen at the Antarctic Snowcap Station and somehow letting Polly die - which also leads to Ben leaving (The Tenth Planet), the Doctor was fearfully reluctant to regenerate when he crossed paths with one of his future incarnations (Twice Upon a Time), who is similarly reluctant to regenerate. The events of the episode convince both Doctors to go through with their regenerations. After returning to his TARDIS, the Doctor, alone, collapsed and regenerated for the first time (Regeneration).

Personality
From the beginning, the Doctor was a mysterious figure. He appeared to be a frail old man and yet was possessed of unexpected reserves of strength and will. He obviously held tremendous knowledge of scientific matters, and yet was unable to pilot his TARDIS time ship reliably; his granddaughter Susan explained this by saying that her grandfather was "a bit forgetful"; but the TARDIS required expert piloting and guidance by the Doctor. Its systems would often break down, especially the navigational systems. This, combined with the fact the TARDIS was actually designed for six pilots, would explain the difficulty the Doctor encountered in piloting it correctly. He was abrasive, patronising, and cantankerous towards his human travelling companions, yet shared a deep emotional bond with his granddaughter Susan. He also harboured a streak of ruthlessness, being willing to lie—and in one case attempt to kill—to achieve his goals. Initially, he distrusted his first two human companions, Ian Chesterton and Barbara Wright, who were forced on him. Over time, however, as they shared adventures together, he grew closer to them, and the TARDIS crew came to share almost a family bond. When proven wrong after accusing Ian and Barbara of sabotaging the TARDIS, the Doctor humbly apologised, especially after seeing that Barbara had been hurt by his accusations. The Doctor realised he could rely on Ian and Barbara, sealing a friendship which lasts until their eventual departure from the TARDIS, with the relationship between the Doctor and Barbara being mutually respectful and increasingly affectionate.

Eventually, the Doctor began to enjoy his travels through time and space, taking people along for the ride and was always reluctant and sad to see them go, even when he knew it was for their own good. The Doctor's personality mellowed, and he evolved into the more familiar grandfatherly figure that children loved. The initially irascible and slightly sinister Doctor quickly mellowed into a more compassionate figure. He was protective of the young women he took on as companions; they reminded him of his granddaughter, Susan.

William Hartnell described the Doctor as "a wizard", and "a cross between the Wizard of Oz and Father Christmas". One quirk of the First Doctor was his tendency to become occasionally tongue-tied and stumble over words. Sometimes this was a deliberate acting choice: William Russell recalls that it was Hartnell's idea for the Doctor to get Ian Chesterton's surname wrong, calling him "Chesserman", "Chatterton" and even "Charterhouse". This character choice also gave the series' producers the ability to use takes in which Hartnell flubbed his lines. Due to the series' tight production schedule, it was rarely possible to reshoot such scenes and dubbing the dialogue was usually not an option. Hartnell suffered from undiagnosed arteriosclerosis, which affected his ability to remember lines, increasingly so as his time on the series progressed.

In "Twice Upon a Time", the Doctor expressed to a variation of his future companion Bill Potts that he had left Gallifrey, among other reasons, to investigate why good prevails in a universe where evil would seem to have so many advantages. As Bill reflected that none of the First Doctor's future incarnations recognized this fact, the Twelfth Doctor summarized that he and his incarnations were the reason for the universe's balance between good and evil.