Kaley Cuoco has admitted some of 'The Big Bang Theory' guest stars struggled on set.

Kaley Cuoco

Kaley Cuoco

The 35-year-old actress - who played Penny in the hit comedy from 2007 to 2019 - revealed how the format proved challenging for certain performers who weren't used to working on a sitcom.

Speaking to Elizabeth Olsen for Variety magazine, she said: "Obviously, that’s my whole life. Especially with 'The Big Bang Theory', we’d have these guest stars come on, and some of them were wonderful dramatic actors or whatever, and they would feel so lost for a while.

"It really is so musical. Because I grew up with it, and I did it for so long, it’s so natural for me. It’s very different if you haven’t done it."

Kaley also recalled her introduction to working on television and recalled the vital lesson her late co-star John Ritter taught her on '8 Simple Rules... For Dating My Teenage Daughter', which ran from 2002 to 2005.

She added: "My first show was with John Ritter, who was my entire world.

"I remember conversations when I was 15 years old where he said, 'You have to remember when you’re on a set, it’s like a tree. Number one’s here, and any way you act is all trickling down that tree.'

"You can be a boss, you can be a great actor, you can get work done, but you can just be nice. People are missing that."

She carried that mindset into shooting 'The Flight Attendance', which she stars in as well as serving as executive producer.

She explained: "It was such a responsibility in my eyes, what that tone was going to be. It all came from me.

"When I came there in the morning, the things that came out of my mouth, they’re watching me, and I know that. It felt also like such a privilege."