What The Big Bang Theory cast looked like at the start of their careers

From Kaley Cuoco and Jim Parsons to Mayim Bialik and more

We love rewatching episodes of The Big Bang Theory. The popular sitcom, which debuted in 2007, follows a group of geeks, including a NASA engineer, an astrophysicist and two physicists, and their lives both in and out of the lab.

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The Emmy award-winning series made household names out of its stars, but have you ever wondered how they got their start in TV? Keep reading to find out more about the incredible cast and their first on-screen roles...

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Johnny Galecki as Leonard Hofstadter 

Leonard is the glue that holds the gang together and is played by actor Johnny Galecki. Johnny landed his first acting gig aged 7 when he was cast in CBS miniseries Murder Ordained. As a kid, he also starred in National Lampoon's Christmas Vacation and the series Blossoms and American Dreamer. 

Johnny Galecki plays Leonard

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Jim Parsons as Sheldon Cooper 

Jim Parsons was born and raised in Texas, just like his character, the awkward but lovable Sheldon Cooper. He relocated to New York in his early twenties to pursue a career in acting and secured a few minor roles before landing the part on the sitcom. One of his earliest roles that caught the attention of viewers was in an advert for Quiznos.

Jim Parsons played minor roles before landing The Big Bang Theory

Kaley Cuoco as Penny 

Kaley Cuoco takes on the role of Leonard and Sheldon's neighbour, Penny. Like her co-star Johnny, she also started acting as a youngster and was cast at the age of 10 to play a young Karin Carter in the 1995 action thriller Virtuosity. Not long after, she was cast on the sitcom Ladies Man and The Brady Bunch film Growing Up Brady. 

Kaley Cuoco began acting as a child

Kunal Nayyar as Raj Koothrappali 

Hapless Raj is played by Indian actor Kunal Nayyar. While studying business at university, Kunal took an interest in acting and found work doing American television ads and plays.

While his only television credit prior to The Big Bang Theory is a small role on NCIS, he gained attention for his role in the play Huck & Holden, where he portrayed an Indian exchange student.

 Kunal Nayyar plays Raj

Simon Helberg as Howard Wolowitz 

Playing Howard is Simon Helberg, who started his career as one part of a comedy duo with Drunk History creator Derek Waters. Before The Big Bang Theory, he appeared on the sketch comedy series MADtv as well as Sabrina the Teenage Witch and Arrested Development. 

Simon Helberg started his career in a comedy duo

Mayim Bialik as Amy Farrah Fowler 

Mayim Bialik joined the cast in season three as neuroscientist Amy. In real-life, Mayim began life as a child actress, with roles in MacGyver and Blossoms, but took a break from acting to study for a doctorate in neuroscience.

Mayim Bialik studied neuroscience during a break in her acting career

Melissa Rauch as Bernadette Rostenkowski-Wolowitz

Howard's unlikely love interest Bernadette is played by Melissa Rauch, who actually began her television career in presenting roles. She was a regular contributor to VH1's Best Week Ever before being cast in Australian comedy Kath & Kim and the short-lived Lily Tomlin-led series 12 Miles of Bad Road.

Melissa Rauch plays Bernadette

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