Doctor Who is a British science fiction television series that depicts the adventures of a time-traveling alien known only as "The Doctor". Originally premiering in 1963, it is listed in the Guinness Book of World Records as the longest running science fiction television series in history though with breaks in production.
- Sheldon's Saturday morning ritual includes getting up at 6:15 am and watching Doctor Who on BBC America. This morning ritual was once disrupted when Penny crashed out on the guys' couch.
- A replica of a Dalek (one of the Doctor's most famous adversaries) is sometimes visible on one of the shelves in Leonard and Sheldon's living room.
- In some shots of the comic book store, a poster of an exploding TARDIS appears on the wall. This is a replica of a painting, "The Pandorica Opens", which in the Doctor Who mythology was painted by Vincent Van Gogh. The painting figures prominently in the two-part series 5 finale, "The Pandorica Opens" and "The Big Bang".
- In the season 4 episode "The Justice League Recombination," Stuart wears the costume of the Fourth Doctor (one of the most famous incarnations, played by Tom Baker) during the New Year's Eve party.
- In the season 5 episode "The Beta Test Initiation," Sheldon, Leonard, Penny and Amy are watching an episode of Doctor Who (either "Silence in the Library" or "Forest of the Dead", both of which take place during the time of the tenth incarnation of the Doctor, played by David Tennant) at Sheldon and Leonard's apartment. When Penny states that her idea of a date with Leonard was not watching Doctor Who and Amy notes the Doctor's fondness for contemporary London, Sheldon kicks Penny out of going to Who-Con and threatens to do the same to Amy.
- In the season 7 episode "The Convention Conundrum," Sheldon reacts to not going to Comic-Con by attempting to hold his own convention. Matt Smith, who played the Eleventh Doctor in series 5 through 7, is on his list of science fiction icons to invite.
- In the season 6 episode "The Holographic Excitation," Sheldon's list of couple's costumes he likes includes "The Doctor & A Dalek." Raj gets a TARDIS photo booth for Stuart's Halloween party, leading Sheldon to call it a "major rager." Later, Leonard (as Doctor Albert Einstein) "explains the theory of relativity" to Penny (who is dressed as a sexy cop) in the photo booth (twice!).Note: Penny's costume may be a reference to (A) Eleventh Doctor companion Amy Pond (played by Karen Gillan), who wore a "sexy cop" costume in her first episode, "The Eleventh Hour", or (B) the TARDIS itself, which according to the episode "The Doctor's Wife" likes to be known as "sexy."
- In the season 7 episode "The Romance Resonance," a line in the song "If I Didn't Have You" contains the lyrics "I'd be Doctor Who without the TARDIS." Later, Leonard can be seen wearing a t-shirt featuring the Seal of Rassilon, a Doctor Who motif.
- At the end of the season 7 episode "The Itchy Brain Simulation", as Raj is shouting at himself in the mirror, a Dalek "To victory!" poster from Doctor Who's Victory of the Daleks is seen in the background.
- In the season 7 episode "The Proton Transmogrification," Sheldon tells Professor Proton in his dream that he's had to say goodbye to eleven Doctor Who's. This refers to the times that the Doctor has "regenerated", a process that restores his body to health but completely alters his appearance and personality (developed by the producers in 1966 as a way to replace First Doctor actor William Hartnell with Second Doctor actor Patrick Troughton, and subsequently used whenever the actor playing the Doctor leaves the show). The most current regeneration was from Matt Smith's Eleventh Doctor to Peter Capaldi's Twelfth Doctor in the 2013 Christmas episode "The Time of the Doctor".
- In the season 8 episode "The Skywalker Incursion", Bernadette and Howard have a dispute over whether or not to sell off Howard's TARDIS. They later agree to decide using a game of table tennis with their friends competing. Bernadette bribes Raj by telling him having the TARDIS at his apartment, with the backdoor facing his apartment door, it would look as though it was "bigger on the inside". Penny mentions that the Doctor was from Gallifrey and it was sad that she knew that. In the end Amy wins the TARDIS and puts it in her bedroom, where Sheldon enters dressed as the Fourth Doctor and mentions he's being chased by Daleks and that he needed to reset the time circuits, but then claims he left his sonic screwdriver behind and runs back to get it. Amy had hoped that Sheldon would have stayed in her bedroom.
- A cardboard cutout of a variant of the Drone Paradigm Dalek that was seen in The Dalek Parliament in the episode: Asylum of the Daleks can sometimes be seen in the back of Stuart's Comic Book Store. Mainly from Season 6 onwards because the episode aired in 2012.
Actors who have portrayed the Doctor
William Hartnell - First Doctor (1963–66, 1972-73)
Richard Hurndall - First Doctor (1983's "The Five Doctors")
David Bradley - First Doctor (2017's "The Doctor Falls" and "Twice Upon a Time")
Patrick Troughton - Second Doctor (1966–69, 1972–73, 1983, 1985)
Jon Pertwee - Third Doctor (1970–74, 1983, 1993)
Tom Baker - Fourth Doctor (1974–81, 1993)
Peter Davison - Fifth Doctor (1981–84, 1993, 2007)
Colin Baker - Sixth Doctor (1984–86, 1993)
Sylvester McCoy - Seventh Doctor (1987–89, 1993, 1996)
Paul McGann - Eighth Doctor (1996's Doctor Who and 2013's "The Night of the Doctor")
John Hurt - War Doctor (2013's "The Day of the Doctor")
Christopher Eccleston - Ninth Doctor (2005)
David Tennant - Tenth Doctor (2005–10, 2013)
Matt Smith - Eleventh Doctor (2010–13, 2014)
Peter Capaldi - Twelfth Doctor (2013–17)
Jodie Whittaker - Thirteenth Doctor (2017-present)
Additionally, many of the actors who portrayed the Doctor reprised their roles in various Doctor Who audio plays from Big Finish Productions, along with actors who had portrayed their companions over the years (from both the "classic era" and the 2005 revival).