The stars of ‘The Big Bang Theory’ are overachievers in their extra curricular activities

For the cast of “The Big Bang Theory,” the CBS sitcom has been the longest job any of them has held in fickle and unpredictable Hollywood.

And, sure, appearing in twentysomething episodes a season can be time-consuming, but it hasn’t stopped the actors — Jim Parsons, Johnny Galecki, Kaley Cuoco, Simon Helberg, Kunal Nayyar, Melissa Rauch and Mayim Bialik — from venturing outside the show’s home base on the Warner Bros. lot to pursue other ventures. And those extracurricular activities include appearing in Broadway plays, launching websites, starting production companies and acting opposite Meryl Streep.

Here’s a look at some of the side projects the cast has taken on:

Jim Parsons (Sheldon)

"The Big Bang Theory" catapulted Parsons, a longtime theater nerd, to mainstream fame. But he hasn't left his theater roots behind. Parsons is returning to Broadway for the revival of "The Boys in the Band," produced by Ryan Murphy ("Glee") and David Stone ("Wicked"). He has also performed in the plays "An Act of God," "Harvey" and "The Normal Heart,” the latter of which he also starred in for the HBO adaptation. On the producing side, the four-time Emmy winner’s work is just as diverse, including the docuseries “First in Human,” the “Big Bang” spinoff “Young Sheldon” — both of which he also narrates — and the upcoming drama “A Kid Like Jake,” in which he also stars opposite Claire Danes. In 2017, he added radio host to his resume with the SiriusXM talk show “Jim Parsons Is Too Stupid for Politics.” Next up? Parson’s That’s Wonderful Productions recently optioned the film rights to Michael Ausiello’s memoir “Spoiler Alert: The Hero Dies,” with Parsons attached to star. “We’re 11 years on the show now and I still don’t have people knocking down my door to get me to do their things,” Parsons says. “It’s just the right thing here and there that comes my way, and so it’s been a very organic process in the way for me — outside opportunities have changed or grown in their own natural, not-too-fast way along with the success and longevity of the show.”

Johnny Galecki (Leonard)

The former “Roseanne” star — who made a return appearance on that show earlier this season — has produced everything from a documentary short (2013’s “This Is All of Us”) to movies (2018’s “The Cleanse”). This past television season, Galecki produced the CBS comedy "Living Biblically.” Although it was taken off the schedule after just eight episodes, the TV veteran is already eyeing his next act: a science prank show called “SciJinks,” which he will host and produce for Discovery and Science Channel. “There’s such a luxury in being able to explore a single character for 250-plus episodes,” Galecki says of “The Big Bang Theory.” “And, then, of course, it’s changed all of our lives, and the lives of our families. It certainly opens up doors for other things. I think, at this point, for everyone involved, it is important to branch out. It’s very refreshing to work with other people, to play other characters in our extra time because it serves the show when you come back to it.”

Kaley Cuoco (Penny)

Cuoco first dipped her toes in producing with the 2014 movie “Authors Anonymous,” in which she also starred. However, she’s looking to make a more concentrated effort behind the camera, having just launched her own production company, Yes, Norman Productions, in October. Yes, Norman Productions landed a multi-year deal with Warner Bros. TV, the studio that also produces “Big Bang.” The first project on the development slate? A limited series based on the novel "The Flight Attendant,” in which she also hopes to star. “Everyone wants to be on a series that’s going well — that’s just completely obvious,” Cuoco says. “That weekly paycheck and the opportunity to do other things, it’s a total blessing.”

Simon Helberg (Howard)

Helberg and his wife, Jocelyn Towne, co-directed the romantic comedy "We'll Never Have Paris," which Helberg also starred in. He and his wife then signed a two-year production deal with Warner Bros. TV in 2015 to develop new series through their production company, Wildline Entertainment. They recently sold a multi-camera CIA comedy titled “Need to Know” to CBS. Helberg also received a Golden Globe nomination for his widely praised performance in the 2016 Meryl Streep film “Florence Foster Jenkins.” “ ‘The Big Bang Theory’ has been the place where I get to practice every day as an actor,” Helberg says. “Nothing compares to standing opposite another person onstage in front of people, or in front of camera, and I do it every day. I learn, I feel defeated on an hourly basis — and I would never trade it or what it has made possible for me.”

Kunal Nayyar (Raj)

Nayyar landed his breakthrough role on "The Big Bang Theory" just a year after graduating from Temple University in Philadelphia. Since then, he’s lent his voice to animated series like "Sanjay and Craig" and Dr. Pakij in "Fantasy Hospital.” On the stage, Nayyar starred opposite Jesse Eisenberg in the play “The Spoils,” which transferred from off-Broadway to London’s West End in 2016. The actor also published a book about his career in 2015, titled “Yes, My Accent Is Real.” “When I travel all over the world and people come up to me and say how much [“The Big Bang Theory”] changed their lives — that’s amazing,” Nayyar says. “We get kids who come here and we make them laugh until their dying days and that’s enough credit. You show up, and you do your job, and you go home. I’m very lucky and I’ve had a very, very good life because of it.”

Melissa Rauch (Bernadette)

Rauch has lent Bernadette's recognizable, high-pitched voice to animated series. She has voiced characters in children's programs such as “Jake and the Never Land Pirates,” “Star vs. the Forces of Evil" and "Sofia the First.” She also earned strong reviews for her turn in 2015’s "The Bronze," a comedy film Rauch wrote with her husband about a retired Olympic gymnast. “This really is such a wonderful place to work,” Rauch says. “Before this, I was going from job to job — this is my first home as an actor. I never had that consistency. And I didn’t know if I wanted it. It’s something I am so, so grateful for. I’m a writer — my husband and I write together. So, knowing I have these hiatus where we can work towards and be like, ‘OK, what project can we self-generate to work on’ … I’m so grateful that being on this show gives me that opportunity.”

Mayim Bialik (Amy)

Bialik is the ultimate multitasker. After starring in the popular ’90s sitcom "Blossom," she graduated from UCLA and went on to get her PhD in neuroscience, which she completed in 2007, the same year "The Big Bang Theory" premiered. During her stint on “Big Bang,” Bialik has also written four books on subjects such as attachment parenting and vegan cooking. Her next, “Boying Up: How to Be Brave, Bold, and Brilliant,” will be released this month. And she founded the lifestyle website GrokNation.com. “I don’t have any place I’d rather be — than working on ‘The Big Bang Theory,’” Bialik says. “For me, it is the dream of an actor’s lifetime, to be in this kind of situation. I write. I have my fourth book coming out in May. And I will continue to write. I have a website. I’m very dedicated to GrokNation, and I make videos for YouTube and I do charity work. I do a lot of other things.Mostly, I raise my kids. My life is about doing what I need to do to be the best mom I can be, no matter what my work is.”

MORE: What the remarkable run of 'Big Bang Theory' means for Hollywood — and the show's cast and crew

Times staff writers Alejandra Reyes-Velarde and Kate Stanhope contributed to this report.