Doctor Who is a British science fiction show created by Sydney Newman, C.E. Webber, and Donald Wilson for the BBC. Its first iteration ran for twenty-six seasons from 23 November 1963 to 6 December 1989 for twenty-six seasons. Its current run began on 26 March 2005. On 12 May 1996, a TV-movie pilot for a new series was co-produced between the BBC and FOX, but poor American ratings stopped the show from being commissioned fully. As of 2017, the series is produced by BBC Wales, though BBC America has co-produced several recent episodes filmed in the United States. All iterations are considered to be part of the same continuity.
Doctor Who follows the adventures of The Doctor, an alien scientist (real name unknown) from a race known as the Time Lords who travels through time and space in his time machine, The TARDIS (Time and Relative Dimensions in Space), righting wrongs and defeating villains. He is usually joined by one or more companions, usually humans, who aid him in his adventures and allow an outside viewpoint on The Doctor's actions. The series began in 1963 as an educational show, with stories split between historical tales and science-fictional ones, but the sci-fi stories - aided by the popularity of the Daleks, the monsters who would become The Doctor's ultimate foes - quickly took over the series.
The show celebrated its 50th anniversary in 2013. A prime reason for its longevity is the concept of regeneration. Should Time Lords suffer a mortal injury, or simply grow too old, their body can regenerate into a totally new appearance and personality, but retaining most memories, experience and wisdom of previous incarnations. This concept was introduced in order to allow the series to recast its lead actor and work the change into the story line. To date, there have been 13 canonical doctors. In order, their actors were: William Hartnell (1963-1966), Patrick Troughton (1966-1969), Jon Pertwee (1970-1973), Tom Baker (1974-1980), Peter Davison (1982-1984), Colin Baker (1984-1985), Sylvester McCoy (1987-1989, 1996), Paul McGann (1996; 2013), John Hurt (2013, as a "secret" incarnation known as the War Doctor), Christopher Eccleston (2005), David Tennant (2005-2010), Matt Smith (2010-2013), and Peter Capaldi (2013-present). Due to the unique nature of the character, past Doctors have made occasional return appearances alongside the current Doctor, most often in special anniversary episodes, such as 2013's The Day of the Doctor which united incumbent Matt Smith with David Tennant, a previously unknown incarnation played by John Hurt, and also featured cameos by all other past Doctors as well as a future Doctor played by Peter Capaldi.
The series is extremely fluid, allowing for multiple interpretations of its tone and content. Over the years it has featured light-hearted comedies, eco-parables, gothic horror, hard science fiction, historical adventures, Avengers-esque spy stories and many more genres. Likewise, the character of The Doctor changes enormously from incarnation to incarnation, with variations including a suave, karate-chopping action hero (Jon Pertwee); a goggle-eyed, crazy bohemian (Tom Baker); a Machiavellian schemer (Sylvester McCoy); a stern, scarred war veteran (Christopher Eccleston and John Hurt); and a geeky, tweedy scientist (Matt Smith). In this way the character is able to appeal to new generations time after time, and reflect attitudes of the times.
- K-9 and Company was a 1981 pilot episode for a spin-off series starring two of The Doctor's companions, investigative journalist Sarah Jane Smith and robot dog K-9. The BBC changed its mind about commissioning a series before production of the pilot was completed, but allowed it to air as a one-off holiday special.
- The Sarah Jane Adventures was a more successful attempt on the same idea and began after Sarah Jane and K-9 were reintroduced in the 2006 Doctor Who episode "School Reunion". It ran from 2007-2011, when star Elisabeth Sladen passed away and the series was cancelled as, unlike with the Doctor, regenerating Sarah Jane was simply not an option.
- K-9 was a semi-official spin-off unconnected to the above two shows, instigated by K-9's original creator, Bob Baker, and producer Paul Tams. Though it isn't as directly connected as the other spin-offs as it is not produced by the BBC (in-story reasons, including K-9 losing part of his memory, mean that he cannot remember his adventures with The Doctor), there was one definitive reference to its parent series. In "The Curse of Anubis", a Sea Devil, a Mandrel and an Alpha Centaurean - all first seen in Doctor Who - are seen among the slaves of Anubis. An image of the TARDIS is also seen in one episode. The original K-9 voice actor, John Leeson, continued to play the role. The show aired its first season in 2010; as of 2014 a second season is technically still in pre-production.
- Torchwood was a (theoretically) adult spin-off of Doctor Who, beginning after the 2006 season of the series, which introduced Torchwood as a taskforce of alien investigators funded by the British royal family. Its main character, Jack Harkness (John Barrowman), was introduced in the Doctor Who episode "The Empty Child"; another character, Dr Toshiko Sato (Naoko Mori), first appeared (briefly) in the Doctor Who episode "Aliens of London". Torchwood lasted two seasons, then returned for a five-episode miniseries (Torchwood: Children of Earth) and a 10-episode series co-produced between BBC and the US channel Starz (Torchwood: Miracle Day), which aired in 2011. A fifth season has yet to be commissioned as of 2014; technically, the show is not cancelled, but on hiatus pending creator Russell T Davies' decision on future production.
- Class spun off from Doctor Who and is set in Coal Hill Academy. The Twelfth Doctor makes an appearance.
- Between 1987 and the late 2000s, a number of independent companies including Reeltime Pictures and BBV produced made-for-video spin-off films featuring characters licensed from their creators. No reference to the Doctor or the TARDIS was ever allowed, but these productions were nonetheless considered "official". The most notable of these was the 1995 production Downtime, which was a sequel to the two Great Intelligence storylines of the Patrick Troughton era (and, retroactively, this made this also a sequel to the 2012 episode "The Snowmen" and the 2013 episodes "The Bells of Saint John" and "The Name of the Doctor"). The characters of Sarah Jane Smith, Brigadier Lethbridge-Stewart and Victoria Waterfield from the original series were played by their original actors, and a character name Kate Lethbridge-Stewart was introduced; this character became officially canon when she crossed over to the main series with 2012's "The Power of Three". Other productions of note include Daemos Rising (again featuring Kate), Shakedown: The Return of the Sontarans, Zygon: When Being You Isn't Enough, Wartime, Auton (a trilogy), and Mindgame.
- One independent spin-off worth noting separately is P.R.O.B.E., a series of five films produced in the mid-1990s featuring the adventures of a Torchwood-like organization run by Dr. Elizabeth Shaw, former companion of the Third Doctor, played by the original actress, Caroline John.
- Since 2000, Big Finish Productions has been producing BBC-licensed audio dramas based upon Doctor Who. Aside from stories featuring classic-era Doctors, the company has also launched numerous spin-off series focusing on characters, alien races, and locations featured in the series. Spin-offs include Gallifrey, Counter-Measures, Jago & Litefoot, Dalek Empire, I, Davros, Cybermen, Graceless, Vienna, Charlotte Pollard, and The Adventures of Professor Bernice Summerfield. The audio dramas were confirmed as being canonical in the 2013 mini-episode The Night of the Doctor, in which the Eighth Doctor recited the names of all of his audio drama companions before regenerating into the War Doctor. Owing to Big Finish's Westphall-like interconnections, this technically canonized all of the company's audio drama output based on Doctor Who.
Westphall connections in Doctor Who
- In "Ghost Light", the Doctor says, 'Who was it said Earthmen never invite their ancestors round to dinner?' The person who said this, in fact, was not a person at all but The Hitchhiker's Guide to the Galaxy itself (that is, the book featured in the series).
- In "Destiny of the Daleks", The Doctor, pinned down by fallen rubble, passed the time by reading Oolon Colluphid's Origins of the Universe. Some of Oolon Colluphid's other books - Where God Went Wrong, Some More of God's Greatest Mistakes, Who is This God Person Anyway?, Well That About Wraps it Up for God, Everything You Ever Wanted To Know About Guilt But Were Too Ashamed To Ask, and Everything You Never Wanted To Know About Sex But Have Been Forced To Find Out - were mentioned in The Hitchhiker's Guide to the Galaxy.
- In the 1950s, British science fiction writer Nigel Kneale created the character of Professor Bernard Quatermass, who worked for the British Experimental Rocket Group. Although Kneale was never a fan of Doctor Who, a reference to Quatermass did make it into the show. In "Remembrance of the Daleks", a military advisor remarks to her colleague, Alison, 'I wish Bernard (Quatermass) were here,' to which Alison replies: 'British Rocket Group's got its own problems.' Years later, in "Planet of the Dead", a scientist uses 'Bernards' as a unit of measurement, mentioning that they're named after Quatermass. Quatermass appeared in three TV series: The Quatermass Experiment, Quatermass II and Quatermass and the Pit.
- In the charity episode "Dimensions in Time", various versions of The Doctor and his companions from across time find themselves trapped in a time loop in Albert Square, the setting for British soap opera EastEnders. During the course of the episode they meet and interact with several EastEnders characters.
- At the end of "The Christmas Invasion", The Doctor mentions meeting Arthur Dent, the protagonist of The Hitchhiker's Guide to the Galaxy. (It is unclear, however, whether he is referring to Dent as a fictional character in this case.)
Westphall connections to Doctor Who
- In Red Dwarf "Thanks for the Memory", the TARDIS can be seen in the docking bay as Starbug takes off.
- In Chelmsford 123 "Arrivaderci Roma", the Doctor's time machine, the TARDIS, materialises in the background. The Doctor exits, looks around, confused, then gets back in and the TARDIS dematerialises. This is especially notable as the show was produced for, and shown on, Channel 4 - not a BBC channel. The Doctor was played by an unnamed actor and was visible only in silhouette.
- In Red Dwarf "Thanks for the Memory", the TARDIS can be seen in Red Dwarf's docking bay as Starbug takes off. It was added by FX man Mike Tucker, who is a fan of the show.
- In Sherlock "The Hounds of Baskerville", The TARDIS can be seen on the top of the hollow as Henry runs away. Sherlock is produced and written by Steven Moffat and Mark Gatiss, who also work on the Doctor Who revival series, with Moffat being the current producer and showrunner for both programs.
- In The Librarians "And the Final Curtain", the TARDIS and Doc Brown's DeLorean from Back to the Future were in the Library's Time Travel device room.
- The Doctor - the Tom Baker model - has appeared multiple times in both The Simpsons and Futurama, usually as a background character. However, because these shows are animated, they don't count as part of the Westphall multiverse.
- In Doctor Who, many main villains, such as the Great Intelligence and Valdemar, have been stated to be Great Old Ones, a species that includes Cthulhu and other Elder Gods from the Cthulhu Mythos. The Great Intelligence has been explicitly identified as Yog-Soggoth. Although the Cthulhu Mythos is not on television and thus not in the Multiverse, it has had several crossovers with the Conan the Barbarian series.
- The Big Finish audio dramas franchise has produced several stories that crossover with Sherlock Holmes and The Picture of Dorian Gray, but these stories are not on TV and do not count.
- In spin-off literature a number of connections have also been made, including Sherlock Holmes again (who appears as a character in several novels).
- IDW Publications, producers of Doctor Who comic books from 2008 to 2013, published an officially sanctioned mini-series crossover with Star Trek: The Next Generation.