Jim Parsons
Jim Parsons plays Sheldon Copper in The Big Bang TheoryVALERIE MACON/AFP/Getty Images

CBS star Jim Parsons opened up about the much-anticipated The Big Bang Theory spin-off series Young Sheldon while appearing on Watch What Happens Live with Andy Cohen on 8 May.

Explaining how he came up with the idea, Parsons told host Cohen, "It's like an origin story. I was trying to come up with an idea for a show, and we had this idea about my little nephew, who is really smart, down in Texas. "

"My family is pretty average – no offense to them, but they're very normal, and he's very smart. One thing led to another and I thought, 'This could be Sheldon,'" he added. The 44-year-old actor brought the idea to The Big Bang Theory co-creator Chuck Lorre, who gave the green light to his idea. "He was like, 'Yes, let's do this,'" Parsons said.

The half-hour, single-camera spin-off will follow the nine-year-old version of Parsons' Big Bang Theory character Sheldon Cooper, attending school in Texas. With the mini-me played by Big Little Lies star Iain Armitage, Parsons will then narrate the show as adult Sheldon, which is set to premiere this fall on CBS Network.

Zoe Perry is set to star as Sheldon's mother Mary Cooper and – in a meta turnout for the books – she is playing a role first brought to life on The Big Bang Theory by her own mother, Laurie Metcalf.

Perry spoke to Entertainment Weekly about filling in her mother's shoes and revealed she still went through a "typical" audition process, "except that there was this other crazy layer to it." The Scandal actress added, "I went in and auditioned for the casting directors and for [executive producers] Chuck Lorre and Steve Molaro. Then, the rest is my lucky history."

As for playing the character, Perry looked to her mother for inspiration. "I did run one of the scenes with her because I was curious to hear her accent doing it. Although I actually didn't have her read the lines because then that would've just stuck in my head. But I made her talk a little bit and I rewatched some of her stuff," the actress admitted.