The Big Bang Theory’s success can be partly credited to the popular culture that its characters are immersed in which is full of both old and current pop culture allusions. Since their interests coincide with those of the viewers, the show successfully avoided some of the typical narrative traps that sitcoms frequently fall into.

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The gang has shown their passion for numerous well-known franchises from the fantasy and science fiction genres over the years which pave way for some unexpected cameos from legendary guest stars.

Star Wars Franchise

One guy is working on his laptop while the other one is playing legos

The 1977 premiere of the science fiction picture Star Wars: Episode IV - A New Hope by filmmaker George Lucas launched the massive Star Wars franchise that has become contemporary pop culture.

Throughout the show, the guys frequently make references to the Star Wars universe, including its stories, characters, and weapons, starting from the Pilot episode with Sheldon (Jim Parsons) mentioning Penny (Kaley Cuoco) may be using Leonard’s (Johnny Galecki) Star War hair product while in the shower. Numerous actors from the franchise have made appearances in the show such as Mark Hamill, James Earl Jones, and Carrie Fisher.

Battlestar Galactica

A girl shows a guy a weird suit in the closet

Battlestar Galactica is first mentioned in the Pilot episode by Sheldon who wants to watch season two of the show after both he and Leonard notice their new neighbor from across the hall, Penny. Leonard's flight suit makes a later allusion to the show in season 1, episode 9, “The Cooper-Hofstadter Polarization”.

Battlestar Galactica is a science fiction franchise developed by Glen A. Larson that follows the remaining humans as they evacuate in the same-name spacecraft while being pursued by the Cylons in search of a new home.

Star Trek Franchise

four guys in costume trying to hitchhike

Gene Roddenberry founded the American science fiction media property known as Star Trek, which debuted as a 1960s television series and swiftly gained a global following in popular culture. Leonard, Sheldon, Howard (Simon Helberg), and Raj (Kunal Nayyar) are all Star Trek aficionados and science fiction nerds, thus, Star Trek references in the show are frequent.

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They are all fluent in Klingon and frequently play the board game Boggle in the language. Moreover, a few actors of the franchise have made cameos during the show’s runtime including Wil Wheaton, Leonard Nimoy, LeVar Burton, George Takei, and William Shatner.

The Terminator Franchise

A guy talking to a girl on the train

The Terminator, played by Arnold Schwarzenegger, is a cyborg hitman sent back in time from 2029 to 1984 to assassinate Sarah Connor (Linda Hamilton), whose unborn child will one day save humanity from annihilation by Skynet, a malevolent artificial intelligence in a post-apocalyptic future. In season 1, episode 10, “The Loobenfeld Decay”, The Terminator is mentioned in the show while Sheldon and Leonard are ascending the stair.

Later on, in season 2, episode 17, “The Terminator Decoupling”, when the guys run into Summer Glau from Terminator: The Sarah Connor Chronicles, Howard, and Raj make advances.

Firefly

three guys talking to each other

Firefly is a space Western drama TV show that is set in the year 2517, following the arrival of mankind in a new star system and the renegade crew of Serenity, a "Firefly-class" starship. In The Big Bang Theory, Firefly is frequently brought up including a section called ‘television and movies’ in Sheldon and Leonard’s roommate arrangement that suggests they will watch Firefly on Friday nights (season 3, episode 22, "The Staircase Implementation").

In addition, in season 7, episode 6, “The Romance Resonance", Howard wrote in his song “If I Didn’t Have You” for his wife, Bernadette (Melissa Rauch) that referenced Firefly, “I’d be Firefly, Buffy, and Avengers without Joss Whedon.

Harry Potter Franchise

a girl dresses in harry potter costume and poses sexily

The Harry Potter film series is based on the J. K. Rowling novels of the same name and chronicles the adventures of Harry Potter (Daniel Radcliffe) and his friends as they attend Hogwarts School of Witchcraft and Wizardry and battle the evil Lord Voldemort (Ralph Fiennes).

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The first reference to Harry Potter was made in season 3, episode 2, "The Jiminy Conjecture" when Raj comments that Harry Potter and the Goblet of Fire was ‘just fine.’ Later on, in season 5, episode 17, "The Rothman Disintegration", Raj spends $25 on eBay for a handcrafted Harry Potter wand which turns out to be a stick.

The Lord of the Rings Franchise

a guy stares terrifyingly at the bald reflection of himself while the other one stares at a ring

The first time The Lord of the Rings was referenced in The Big Bang Theory is when Leonard dresses as Frodo to attend one of Penny’s parties (season 1, episode 6, "The Middle-Earth Paradigm"). Later on, when the guys stumble upon a ring that served as a prop in the movies, they try different methods to win custody of the ring.

Thus, in a dream, Sheldon finds himself transforming into Gollum and conversing with his mirror counterpart as Smeagol (season 3, episode 17, "The Precious Fragmentation"). The Lord of the Rings is a trilogy of epic fantasy action movies set in the fictitious Middle-Earth and follows Frodo Baggins (Elijah Wood) and the Fellowship as they set out on a mission to destroy the One Ring to ensure the death of its creator, the Dark Lord Sauron.

Indiana Jones Franchise

four guys with camping equipments waiting in line

A fictitious professor of archeology named Dr. Henry Walton "Indiana" Jones, Jr. (Harrison Ford), first appeared in the 1981 movie Raiders of the Lost Ark, which launched the Indiana Jones franchise.

In The Big Bang Theory, an Indiana Jones reference is mentioned in season 7, episode 4, “The Raiders Minimization” when Amy (Mayim Bialik) exposes a plot hole in the first installment that ruins Sheldon’s cinematic experience. Moreover, fans also see the guys spend the entire night camped out in anticipation of an extended Indiana Jones cut in season 4, episode 8, “The 21-Second Excitation”.

Back to the Future II

two guys dress for Halloween

The sequel to the 1985 film Back to the Future and the second entry in the series of the same name, Back to the Future Part II is a 1989 American science fiction film directed by Robert Zemeckis. Since the movie takes place in 2015, which is the next year according to the guys, they choose to work on one of the futuristic innovations from the movie such as the hoverboards in season 8, episode 5, “The Focus Attenuation”.

They end up viewing the movie after debating how to create one. Moreover, in season 12, episode 6, “The Imitation Perturbation”, Sheldon dresses as Doc Brown (Christopher Lloyd) from the franchise on Halloween.

Game of Thrones

two guys stares at a sword

Game of Thrones is an American fantasy political drama that is based on George R. R. Martin's fantasy book series A Song of Ice and Fire, which depicts a web of political rivalries among the great families in Westeros.

Many references to the program have been seen in The Big Bang Theory including Sheldon and Leonard purchasing Jon Snow’s (Kit Harrington) replica sword, Longclaw to add to their fantasy sword collection (season 5, episode 5, “The Russian Rocket Reaction”,) or there is an entire episode devoted to the guys viewing an episode of Game of Thrones, in which Stuart appears dressed as Jon Snow (season 9, episode 21, “The Viewing Party Combustion”.).

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