Kaley Cuoco got the surprise of a lifetime when Sharon Stone asked to be cast in "The Flight Attendant" – but it's what happened next that was even more shocking.

Cuoco promoted the series while appearing on "Jimmy Kimmel Live!" on Monday, where she dished about Stone being brought on to play her mother for Season 2 of the HBO Max show.

"She was a fan of the show. She loved Season 1 and heard we were casting my mom and she called casting herself and said, ‘I’d love to do this.' And casting said we had a voicemail from Sharon Stone…I was like this can't be real and found out it was," Cuoco recalled.

The actress said she and Stone filmed "very intense scenes" together and there was one in particular in which Stone wanted to improvise — and ended with the "Basic Instinct" alum slapping Cuoco across the face.

KALEY CUOCO 'DEVASTATED' AFTER 'KNIVES OUT 2' ROLE WENT TO KATE HUDSON OVER HER: 'I CRIED ALL NIGHT LONG'

Kaley Cuoco was stunned when Sharon Stone slapped her not once but three times while filming "The Flight Attendant." (Rich Fury/Rich Polk)

"I think one of our scenes was like 10 minutes long and very emotional. There's a lot of crying. Before we started the scene she sat me down and said, ‘Hey, how do you feel about me touching you in this scene?’ I said, ‘Whatever you want to do Sharon. You are Sharon Stone. You do what you want to do. I’m just so happy you're here." She goes ‘Great,'" Cuoco recalls to Kimmel.

"We do the take and it's this very long emotional scene and at the end of the scene she's supposed to come up and say something very serious to me and walk out. She's supposed to say ‘I like you but I don’t love you very much.' She says this line to me and she grabs my face and she whacks me."

Cuoco called her on-camera reaction "about as real as you could get." 

"So Sharon comes back in and she goes ‘Oh my God, I love you. I didn’t mean to do that it felt right for the scene,'" Cuoco recalls. "I'm like, I just got b----slapped by Sharon Stone."

KALEY CUOCO SAYS SHE WILL ‘NEVER GET MARRIED AGAIN’ FOLLOWING DIVORCE FROM KARL COOK

The slap also took everyone by surprise, Cuoco said, but the star told the crew not to say anything to Stone because she was confident it wouldn't happen twice. "I'm gonna bet money that woman isn't slapping me again. We got the money take," Cuoco recalls telling producers.

However, on the second take, Stone "wails on me again!" Cuoco says, adding that she once again displayed "another incredibly real reaction because I just got slapped a second time."

CLICK HERE TO GET THE FOX NEWS APP

When it came time for the third take, Cuoco recalled, "I'm like, Sharon Stone's not going to slap me a third time. We got it. [The camera] wasn't even on me the last take."

A scene from "The Flight Attendant" Season 1 starring Kaley Cuoco and Zosia Mamet. (Phil Caruso/HBO Max)

"We do the take again she gets right in there…She slaps me again. Three times I got slapped," Cuoco said.

CLICK HERE TO SIGN UP FOR OUR ENTERTAINMENT NEWSLETTER

Ultimately, Cuoco said it was "incredible" acting. She said filming with Stone was "insane but one of the best stories I've ever had."

Sharon Stone will play Kaley Cuoco's onscreen mother in Season 2 of "The Flight Attendant." (Andreas Rentz/Getty Images for ZFF)

She also assured "Flight Attendant" fans that the slap made it into an upcoming episode. 

"She was one of the most wonderful people though. It was as real as it could get," Cuoco said.