Doctor Who is a British science fiction TV show that began all the way back in 1963, created and produced by the British Broadcasting Company (BBC). It was created by 3 folks at the BBC: Sydney Newman, C.E. Webber, and Donald Wilson. Originally intended to be an educational show for children, it quickly created a mind of its own and grew into the spunky, often absolutely goofy sci-fi we know it as today. The show's original run lasted from 1963 through 1989 with a TV film in 1996. In 2005, Doctor Who officially came back, and has been running ever since.

The show centers around the titular Doctor, an alien known as a Time Lord from the planet Gallifrey. It follows their adventures through time and space, often occumpanied by one or more companions whilst doing so. The Doctor gets around the universe in a bright blue 60's police box known as the TARDIS (Time And Relative Dimensions In Space) that has become essentially the show's logo--even actually becoming part of the logo during the late Smith-early Capaldi era.

One of the main facets of the Doctor is that they can periodically regenerate their body when injured or old enough. This is the reason the show has lasted as long as it has, as actors can be switched out when needed. Fourteen actors have played the main incarnations of the Doctor, with two other actors playing auxilliary incarnations. These actors are, in chronological order: William Hartnell (1963-1966), Patrick Troughton (1966-1969), Jon Pertwee (1970-1974), Tom Baker (1974-1981), Peter Davidson (1982-1984), Colin Baker (1984-1986), Sylvester McCoy (1987-1989), Paul McGann (1996, 2013), Christopher Ecclecston (2005), David Tennant (first time, 2005-2010), Matt Smith (2010-2013), Peter Capaldi (2014-2017), Jodie Whittaker (2017-2022), David Tennant (second time, 2023), and Ncuti Gatwa (2023-present). The two other actors are John Hurt, who played the War Doctor (an incarnation between McGann's 8th and Ecclecston's 9th) in 2013 and Jo Martin, who played the Fugitive Doctor during Whittaker's run beginning in 2020.

While the original run included many other Time Lord side characters, including characters like Romana and the Rani, no other Time Lord was generally more important than the Master. The Master was the Doctor's foil, your classic exact opposite to the hero type villain. However, in the 2005-onwards run of the show, the Doctor and the Master's relationship was further expounded on by retroactively having them been formerly very, very close friends. The actors to have played the Master include: Roger Delgado (1971-1973), Peter Pratt (1976), Geoffrey Beevers (1981), Anthony Ainley (1981-1989), Eric Roberts (1996), Derek Jacobi (2007), John Simm (2007, 2010, 2017), Michelle Gomez (2014-2017), and Sacha Dhawan (2020-2022). Gomez's incarnation of the Master is the only one to go by a different title, electing to call herself the Mistress--shortened to Missy--instead.