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The season introduces William Hartnell as the First Doctor, an alien who travels through time and space in his TARDIS, which appears to be a British police box on the outside. Carole Ann Ford is also introduced as the Doctor's granddaughter Susan Foreman, who acts as his companion alongside her schoolteachers Ian Chesterton and Barbara Wright, portrayed by William Russell and Jacqueline Hill, respectively. Throughout the season, the Doctor and his companions travel throughout history and into the future. Historical stories were intended to educate viewers about significant events in history, such as the Aztec civilisation and the French Revolution; futuristic episodes took a more subtle approach to educating viewers, such as the theme of pacifism with the Daleks.

Season One of Doctor Who premiered on November 23rd, 1963. This season contains Fourty-Two episodes.

Milestones this season included not one but two encore appearances by the Daleks; the departure of the original three companions, Susan Foreman, Barbara Wright and Ian Chesterton; and the first appearance of someone else from the Doctor and Susan's home planet, and the first Time Lord enemy to appear.

Season Two of Doctor Who premiered on October 30th, 1964. This season contains Thirty-Nine episodes.

At twelve episodes, The Daleks' Master Plan was the longest story in the show's history until superseded by the fourteen-episode The Trial of a Time Lord in 1986. The season also had the greatest number of different companions (seven) and producers (three). This was the longest season in the history of the franchise to date, at 45 episodes. It also featured the first appearance of actor Nicholas Courtney, although not in his most famous role as the Brigadier. The Daleks' Master Plan also saw the return of Peter Butterworth as the Monk, who became the second Doctor Who enemy to make a return (after the Daleks themselves) to the show. This was also the season of The War Machines, to date the only televised story in which the taboo of never referring to the Doctor directly by the name "Doctor Who" is broken, with the exception of Missy's teasing in World Enough and Time.

Season Three of Doctor Who premiered on September 11th, 1965. This season contains Fourty-Five episodes.

This season was a season of major changes for Doctor Who, including some that have influenced the series and franchise ever since. Most notably, season 4 saw William Hartnell's First Doctor hand off the baton to Patrick Troughton's Second Doctor in the very first regeneration. When Hartnell announced his plans to leave the series, the show's writers came up with the idea of having the Doctor change his appearance and personality. In 1966, while it was not uncommon for actors to change in ongoing TV and film roles, this was possibly the first time a change in appearance was written into the very nature of the character.

Season Four of Doctor Who premiered on September 10th, 1966. This season contains Fourty-Three episodes.

No complete stories from the season were known to have survived until the early-1990s when archivists recovered a complete version of The Tomb of the Cybermen. A second complete story, The Enemy of the World was recovered in 2013, along with a nearly complete recovery of the story that followed it, The Web of Fear. The season is also notable for having Patrick Troughton play a double-role as both the Doctor and Salamander in The Enemy of the World.

Season Five of Doctor Who premiered on September 2nd, 1967. This season contains Fourty episodes.

This season featured the first ever UNIT story, The Invasion, which showcased the return of Brigadier Lethbridge-Stewart. It also featured the first official appearance of Time Lords and the as yet unnamed Doctor's home planet (another member of Susan and the Doctor's race, the Monk, had appeared previously, but without much elaboration and without using the term "Time Lord"). It also marked the tenure of Patrick Troughton as the Second Doctor. It consisted of seven serials and forty-four episodes, including two epic-length storylines: the eight episodes of The Invasion and the ten-episode The War Games.

Season Six of Doctor Who premiered on August 10th, 1968. This season contains Fourty-Four episodes.

It was the first series produced and broadcast in colour and the first set entirely in one time period and almost entirely on Earth (the latter of these factors would later be repeated for Season 26 and Series 1, although in those two cases there was no attempt at an in-universe explanation for confining the Doctor to the planet). Although the series did not have an overall story arc, it did feature a recurring subplot of the Doctor trying to adjust to life as an exile while trying to circumvent the restrictions placed upon him by the Time Lords, and began the process where the Doctor would try to gain more control over his TARDIS. Beginning with this series and continuing for the next few years, most storylines involve the Doctor working with UNIT.

Season Seven of Doctor Who premiered on January 3rd, 1970. This season contains Twenty-Five episodes.

As of 2017, season 8 remains notable for being the season with the most number of regular characters. Not only did it see a new companion in the form of Jo Grant, but it featured a regular enemy — The Master — who was the first regular Time Lord enemy of the Doctor to appear more than twice, and an expanded regular UNIT cast that now included Sergeant Benton and Mike Yates in most episodes. Adding in returning regulars Jon Pertwee and Nicholas Courtney, the regular cast swelled to six.

Season Eight of Doctor Who premiered on January 2nd, 1971. This season contains Twenty-Five episodes.

It was noted for being the beginning of the end of the Doctor's exile on Earth, with the Doctor's TARDIS still under the control of the Time Lords (The Mutants) and restricted freedom (The Curse of Peladon and The Time Monster), as well as UNIT and the Master appearing less frequently in compared to the previous two series. As well as the return of the Daleks and the Ice Warriors, this series also introduced Alpha Centauri, Aggedor and the Silurians' aquatic cousins the Sea Devils.

Season Nine of Doctor Who premiered on January 1st, 1972. This season contains Twenty-Six episodes.

William Hartnell returned in a cameo as the First Doctor and Patrick Troughton in a more substantial role as the Second Doctor in The Three Doctors. This story marked the end of the Doctor's exile on Earth, opening up the series to more off-world adventures and beginning a gradual reduction of UNIT-related stories.

Season Ten of Doctor Who premiered on December 30th, 1972. This season contains Twenty-Six episodes.

It was Jon Pertwee's final season as the Doctor and included, very briefly, the first appearance of Tom Baker as the Fourth Doctor. The Time Warrior, the season opener, introduced Sarah Jane Smith, who was a frequently featured character in the Doctor Who universe decades after her departure in Season 14. The same story also, for the first time, named the Doctor's homeworld as Gallifrey. UNIT also began to be phased out of the series during this season.

Season Eleven of Doctor Who premiered on December 15th, 1973. This season contains Twenty-Six episodes.

All the stories in this season were interconnected, several forming a loose story arc relating to Space Station Nerva. The Cybermen returned to the series for the first time since The Invasion. Genesis of the Daleks, a story which introduced Davros and showed the creation of the Daleks, is one of the most famous of all Doctor Who serials.

Season Twelve of Doctor Who premiered on December 28th, 1974. This season contains Twenty episodes.