Previous roles of The Big Bang Theory stars

Science nerds all over the nation cheered in September 2007 when The Big Bang Theory premiered its first episode on CBS. The sitcom which followed the lives of a socially awkward friend group of science nerds was exactly the refreshing and new kind of show that television needed at the time. Now in the 11th season, The Big Bang Theory has become one of the most-watched, highest-rated comedy series on TV.

Of course, the talented and diverse ensemble of actors and actresses on the show could have something to do with its incredible success. Over the years, many of us dedicated fans have fallen in love with the unique, humorous, adorable, and widely intelligent characters of the series.


Before the cast reached mega fame due to their role on The Big Bang Theory, and before they were considered some of the highest-paying actors and actresses in the industry, many of them were unknown. Although most of the cast members had acting careers prior to the sitcom, their role in The Big Bang Theory was, and possibly will always be, the role they are most-recognized for.

However, we can’t help but go back and relive some of The Big Bang Theory stars’ previous roles that led as stepping stones to their big break.

Johnny Galecki as Leonard Hofstadter

One of the main characters of The Big Bang Theory, Leonard Hofstadter played by Johnny Galecki, is an experimental physicist and best friend/former roommate of fellow physicist Sheldon Cooper. Although Sheldon is known to annoy Leonard, he cares for his friend very deeply and is one of the only people who understands his unique tendencies. Leonard, similar to his group of friends, is extremely intelligent, receiving his Princeton University doctorate at the age of 24. In the first season, he falls for the girl next door, an aspiring actress named Penny. After several seasons of an on and off again relationship status, the couple finally gets it right and eventually ties the knot in the ninth season.

Johnny Galecki as David Healy – Roseanne

Years before his Big Bang Theory fame, a young Johnny Galecki was well-known for a different TV role, on the hugely popular sitcom of the late ’80s to ’90s, Roseanne. He portrayed a character named David Healy, who ends up being the boyfriend and later on husband of Roseanne’s teenage daughter Darlene (played by Sara Gilbert who he would costar with years later on The Big Bang Theory). Little did he know that he would eventually become one of the most successful, and highest-paid comedy actors in television. Recently, the actor went on to reprise his role as David Healy, over twenty years later, on the show’s current 2018 reboot.

Jim Parsons as Sheldon Cooper

Sheldon Cooper, played by Jim Parsons, has been a fan-favorite on the series since the first season. He works at Caltech where he is a theoretical physicist. He is definitely one proud geek, and has a great deal of confidence in himself and his work – perhaps a bit too much at times. He has a tendency to easily irritate those around him with his lack of understanding of humor and sarcasm and obsession with cleanliness and routine. He is currently engaged to neurobiologist Amy, who he has been dating since the fifth season.

Jim Parsons as Tim – Garden State

Prior to his role as the lovable physicist Sheldon, Jim Parsons, who was still a brand new actor at the time, appeared in the widely popular 2004 dark-comedy Garden State. In the film starring Zach Braff and Natalie Portman, Jim played Tim, a childhood friend of Zach’s character Andrew, and a “knight” at a the Medieval Times dinner theater – hence his adorable costume. Of course, this minor role was just a stepping stone for the budding actor, who was about to become a mega star just a few years later.

Simon Helberg as Howard Wolowitz

Simon Helberg portrays the atronaut and aerospace engineer of the group, Howard Wolowitz. Despite his many scientific achievements, his overbearing mother treats him like a child. Earlier in the series, Howard spends a majority of his time at Leonard and Sheldon’s apartment. However, once he meets Bernadette, who was studying for her Ph.D in microbiology and working with Penny at The Cheesecake Factory at the time, he starts spending a lot more time with her. Now they are married and have a daughter named Halley with another one on the way.

Simon Helberg as Seth – Joey

For a couple years leading up to his big break on The Big Bang Theory, Simon Helberg had a recurring role on the Friends spin-off series Joey, starring Matt LeBlanc. Although the show ended up being short-lived, and was canceled after only two seasons – it did help launch Simon’s career, which was still just beginning. Simon played a character named Seth, a friend of Joey’s nephew Michael who just so happens to be a genius aerospace engineer – coincidence?

Mayim Bialik as Amy Farrah Fowler

Mayim Bialik plays another fan-favorite of the series, Amy Farrah Fowler. Amy works as a neurobiologist and is discovered by Howard and Raj during the third season on an online dating site. The two friends thought she would be a perfect match for their complicated and picky friend Sheldon – and they were right. Sheldon and Amy continue to date until season ten, when Sheldon pops the question, asking her to marry him. Luckily, she says yes.

Mayim Bialik as Blossom Russo – Blossom

Mayim Bialik began acting long before her role on The Big Bang Theory. She landed her first big break when she was only 14 years old, as the star of her own TV series, Blossom. In the ’90s sitcom, Mayim plays the titular character, Blossom Russo, an intelligent young girl who lives with her divorced musician father and two older brothers. After five seasons, Mayim slowed down her acting career a bit in order to focus on her studies at UCLA.

Kunal Nayyar as Raj Koothrappali

Another critical part of the geeky gang, Raj, portrayed by Kunal Nayyar, is an astrophysicist originally from New Delhi, India and Howard’s BFF. Earlier in the series, Raj suffers with a serious social anxiety which prevents him from being able to talk to women. However, by the ninth season, he overcomes his fear – so much so in fact that he finds himself in the middle of a messy love triangle between him and two separate women.

Kunal Nayyar as Youssef Zidan – NCIS

Although Kunal Nayyar is now one of the biggest stars in television, he didn’t start off that way. In the role that earned the actor his SAG card, Kunal appeared in an episode of the CBS hit crime-drama series NCIS in 2007, during the show’s fourth season. He played Youssef Zidan, an Iraqi terrorist who ends up getting caught by special agent Gibbs, who plants him a nice punch in the face! It would be only a few months later that he would appear in the pilot of The Big Bang Theory.

Melissa Rauch as Bernadette Rostenkowski-Wolowitz

The adorable yet fierce and slightly intimidating microbiologist Bernadette is first introduced in season three, where she is set up on a date with Howard via Penny. Although she isn’t interested in him at all in the beginning, once she finds out that he too has an overbearing mother – she gives him another chance. Safe to say, the two lovebirds hit it off, getting married in season five and starting a family together shortly after.

Melissa Rauch as Tina – Kath & Kim

Before Melissa Rauch was known as the outgoing microbiologist Bernadette, she had a recurring role in the U.S. version of the popular Australian comedy series about a dysfunctional mother and daughter relationship titled Kath & Kim. Melissa played alongside the show’s stars Molly Shannon and Selma Blair as Tina, Kim’s bubbly best friend who often offers her poor advice. Unfortunately, the series didn’t last more than one season, but luckily for Melissa – she had a better role waiting for her shortly after.

Kevin Sussman as Stuart Bloom

The hilarious Kevin Sussman joined the cast of The Big Bang Theory during its second season as Stuart Bloom. Stuart owns the local comic book shop that the group makes frequent visits to. Stuart is not the happiest person to be around, and is often depressed due to his lack of love life and financial problems. Although he occasionally hangs out with the guys, he often is left feeling like an outsider and is always trying to seek the gang’s approval.

Kevin Sussman as Walter – Ugly Betty

Although Kevin Sussman had already been in quite a few roles before playing Stuart, one of his most well-known TV roles was on the hit ABC comedy-drama Ugly Betty. He portrayed Walter, Betty’s slightly possessive on again off again boyfriend who works at an electronics store. After the first season, he left Betty and the show behind and went on to join the cast of The Big Bang Theory a couple years later.

Sara Gilbert as Leslie Winkle

Sara Gilbert made her first Big Bang Theory appearance early on in the first season, as Leonard’s coworker and love interest Leslie Winkle. She is seen by the group as the female version of Leonard, who even sports the same black-framed glasses and zip-up hoodie sweatshirts. After finding Penny out of his league, he decides to go out on a date with Leslie. In the end, it doesn’t work out, although she does have a brief fling with Howard for a while.

Sara Gilbert as Darlene Conner – Roseanne

Of course, before Sara Gilbert and Johnny Galecki were on-screen lovers in The Big Bang Theory, they were known for their TV romance in Roseanne. Sara played Darlene Conner, the sarcastic and creative middle child of Roseanne, who dates and eventually marries her longtime boyfriend David Healy (Johnny Galecki) and later on has two children with him. Sara is now not only reprising her role on the Roseanne reboot, she is also acting as the show’s executive producer.

Laura Spencer as Emily Sweeney

Raj meets Emily Sweeney, played by Laura Spencer, on a dating site during the seventh season. He falls for her unique sense of humor and love of horror films. The two start to date and get pretty serious until Raj ends it with her in order to pursue a screenwriter/bartender named Claire. Raj eventually finds himself dating both women, until things get out of hand and he has no choice but to say goodbye to them both.

Laura Spencer as Jane Bennet – The Lizzie Bennet Diaries

The lovely Laura Spencer first gained prominence in 2012, after appearing in a YouTube web series adapted from Jane Austen’s romantic novel Pride and Prejudice called, The Lizzie Bennet Diaries. In the show comprised of various vlogs, Laura played Jane Bennet, an overworked and underpaid fashion merchandise coordinator. The show gained a great deal of success, and ended up becoming the first web series to ever win an Emmy, for Outstanding Creative Achievement in Interactive Media – Original Interactive Program.

Kaley Cuoco as Penny Hofstadter

The stunning Kaley Cuoco portrays Penny Hofstadter. She was first introduced in season one as Leonard’s blonde-bombshell of a neighbor who was trying to make it as an actress while working as a waitress. Eventually, she leaves her acting career behind in order to take on a job as a pharmaceutical representative at the same company her friend Bernadette works for. She and Leonard date on and off until getting married in Vegas during season nine.

Kaley Cuoco as Bridget Hennessy – 8 Simple Rules

Kaley Cuoco’s first big TV role was in the ABC sitcom 8 Simple Rules. She had a main role as Bridget Hennessy, the beautiful and at times dim-witted oldest child of Cate (Katey Sagal) and Paul Hennessy (John Ritter). During the second season, Kaley’s TV dad John Ritter suddenly passed away, leaving Kaley, who was always very close to him, completely heartbroken and devastated. In a recent tribute to the late actor on her Instagram page, she wrote, “Still not a day goes by where he doesn’t make me laugh one way or another.”