Since The Big Bang Theory is one of the most successful sitcoms of all-time, many fascinating facts about the TV show have been revealed. For example, fans learned about the gross thing Mayim Bialik did for the show, how hard it was to cast Penny, and why TBBT made Simon Helberg uncomfortable. Similarly, The Big Bang Theory fans also learned that the show once traumatized a former teen star and who Jim Parson’s favorite guest star was.

However, there are some The Big Bang Theory facts that it seems like virtually nobody knows. Some notable examples of that include the facts that Johnny Galecki dated Sheldon’s mom in another show and that Craig Ferguson had an unofficial cameo. Since she only recently talked about it, another rare The Big Bang Theory fact is why one of the show’s forgotten stars left the show.

Who Are The Big Bang Theory’s Forgotten Stars?

When people think of the cast of The Big Bang Theory, the list of people who come to mind is relatively short. Those names are likely to be limited to Johnny Galecki, Jim Parsons, Kaley Cuoco, Simon Helberg, Kunal Nayyar, Mayim Bialik, and Melissa Rauch.

While there is no doubt that those names make up the list of The Big Bang Theory’s main stars, many fans forget that other people were also promoted to the show’s main cast. In fact, there were three other people who were officially credited as series regulars, which means they were part of the main cast.

For most fans, Kevin Sussman has to be The Big Bang Theory’s most obvious forgotten star.

Cast as Stuart Bloom, Kevin first became a part of The Big Bang Theory’s main cast during Season 6. For Season 7, Kevin was demoted back to a recurring role, but he was promoted again for Season 8 and remained a part of The Big Bang Theory’s main cast for the rest of its run.

In August 2012, Deadline published an article about Kevin being promoted to a series regular. According to IMDb, Kevin becoming part of The Big Bang Theory’s main cast allowed him to appear in 84 episodes of the show.

Probably The Big Bang Theory star that viewers are least likely to know was a part of the main cast is Laura Spencer.

Cast as Emily Sweeney, the one-time girlfriend of Rajesh Koothrappali, Laura was officially part of the main cast during Season 9, according to an October 2015 Yahoo! Entertainment article.

Easily the most famous former The Big Bang Theory star that people don’t realize was part of the main cast is Sara Gilbert. Best known for starring in Roseanne and The Conners, Sara also co-hosted The Talk for almost a decade.

As a January 2009 Entertainment Weekly article shows, Sara had been upgraded to The Big Bang Theory’s main cast in 2008. However, after only five months, The Big Bang Theory bosses decided to reverse their decision and the outlet reported that they’d ended Sara’s contract.

Sara Gilbert Recently Revealed Why She Left The Big Bang Theory

According to Sara’s IMDb page, she was last a regular part of The Big Bang Theory’s cast during the second season. After that, Sara appeared in a single The Big Bang Theory episode during the show’s third and ninth seasons. Despite that, in 2025, Sara revealed breaking news about her The Big Bang Theory tenure.

Since Sara was famous by the time she began showing up in The Big Bang Theory episodes, her joining the show was a big deal. In fact, Sara was in a very similar situation as the one Mayim Bialik was in when she showed up on The Big Bang Theory after previously starring in Blossom.

Given that Mayim starred in The Big Bang Theory for years, it would have made sense if Sara had done the same thing. However, Sara stopped appearing regularly and mostly disappeared from The Big Bang Theory.

As an April 2025 AOL article shows, Sara explained what led to her leaving The Big Bang Theory at that time. During an appearance on “The Official Big Bang Theory Podcast,” Sara told that show’s host, Jessica Radloff, that The Big Bang Theory’s writers ran out of things to do with her character, Leslie Winkle.

“I think the writers kind of hit a wall with the character, probably also because she leaves these dynamics quickly, you know, then kind of like, well, what do you do now? She’s wired like that, and she left, and then there’s no more story there, really.”

During the same conversation, Sara revealed another fascinating truth about her The Big Bang Theory departure.

In an ideal world, every actor who leaves a show would walk away feeling good about their tenure. However, the sad truth is that often isn’t the case. Thankfully for her, during the same podcast episode, Sara explained how much she enjoyed starring in The Big Bang Theory while it lasted.

“It was a blast, and I like to work, so I’m always happy to show up.”

To further underline how much she enjoyed acting on the show, Sara told the podcast host that she would have continued starring in The Big Bang Theory if she could have.

While it would have been lovely to see more of Sara on The Big Bang Theory, many fans would likely agree that her character ran its course.