Nicole Kidman's husband, kids helped her prep to play Lucille Ball in 'Being the Ricardos'

Nicole Kidman immediately jumped at the chance to work with Aaron Sorkin on "Being the Ricardos," the Oscar-winning screenwriter's spin on Lucille Ball and Desi Arnaz.

"Then it hit me after I said 'yes,' what I'd taken on and I was terrified," admits Kidman, who co-stars with Javier Bardem in the biopic (in select theaters Friday, streaming on Amazon Prime Dec. 21). Between the accent, physical comedy and extremely dense script, "it was like trying to use everything in your arsenal as an actor. I was going to have to stretch in a massive way."

"Ricardos" is a behind-the-scenes look at one week in the making of the hit 1950s sitcom "I Love Lucy." The awards hopeful was initially met with skepticism over its casting, although both Kidman and Bardem have received mostly strong reviews, with USA TODAY's critic calling the former “terrific.”

Review: Nicole Kidman impresses as TV icon Lucille Ball in Aaron Sorkin's 'Being the Ricardos'

"What I needed was a great dramatic actress with a dry sense of humor and a facility with language, and Nicole has all of that," says Sorkin, who wrote and directed the movie. "And Javier is so charming, so gregarious and impossible not to love."

Kidman, 54, and Bardem, 52, walk us through the process of playing two of history’s most beloved sitcom stars.

Step 1: Binge-research everything.

Once they were cast, the actors had roughly two months of "arduous, really methodical preparation," Kidman says. For both she and Bardem, that meant poring over Ball's and Arnaz's memoirs, watching old footage from the family's archive, and closely studying classic "I Love Lucy" episodes including "Fred and Ethel Fight" and "Lucy's Italian Movie," whose iconic grape-stomping scene they re-create in the movie.

"Binge-watching the show, binge-reading, binge-listening – everything binge," Bardem says. "And then at the moment (of shooting), we had to forget about it and try to relax. (Sorkin) helped me with the anxiety of becoming that person because that's not what he was looking for: He wanted the essence of the people inside those characters."

Step 2: Master the movements.

Ball was "a beautiful clown," with movie-star looks and rubbery limbs prone to pratfalls, Kidman says. The actress practiced her elastic facial expressions and movements at home in her living room, where she'd put on episodes of "I Love Lucy" with husband Keith Urban and daughters Sunday Rose, 13, and Faith Margaret, 10.

"I'd have it up on my TV screen, and I'd have my (movement coach) or my husband or my kids standing off to the side," Kidman recalls. "I would be doing the movements and then looking and going, 'Have I got it?' And it was interesting how it was always like, 'No, be bigger, bigger, bigger!' I would think my eyes were huge or my mouth was wide open, but they'd be like, 'Bigger!' It was incredibly freeing to do it. I really recommend it for anyone as therapy. (Laughs.) Do the grape stomping, it makes you feel good. It can pull you out of a funk."

Bardem and his actress wife, Penelope Cruz, similarly showed the original series to their children: Leo, 10, and Luna, 8.

"My kids loved it," he says. "When I was putting the videos on, they were laughing so much. Some things they weren't understanding because of the language (barrier), but they reacted to the physicality of it all," which helped him understand how important physical comedy was in making "I Love Lucy" entertaining.

Step 3: Learn to play music.

Arnaz was a bandleader on and off screen, meaning Bardem had to learn to sing and play the conga drum. He took lessons over Zoom due to the pandemic, "which is kind of a weird thing." The Spanish actor also had to recreate Arnaz's distinctive Cuban accent.

"He would go a little bit more extreme in the accent on the show because great jokes come out of that," Bardem says. "But he was very much in command of the same energy on and off the show, especially as a producer. I heard private recordings of him talking to colleagues, and you can really hear him owning the room without being pushy. It was really about making everybody understand that he knows what he's doing and you should trust him."

Step 4: Find the voice.

For Kidman, some of the trickiest work was differentiating how Ball, the actress, and Lucy Ricardo, her character, sounded.

Essentially, “they are two roles: She created Lucy Ricardo," Kidman says. “I studied her voice and it was much deeper (in real life). She was much more direct and her behavior was very different to Lucy Ricardo."

To capture Ball’s higher pitch TV timbre, she repeatedly watched the sitcom's famous “Vitameatavegamin” scene, where Lucy gets drunk doing a TV commercial for an unexpectedly alcoholic product.

" 'Vitameatavegamin' was my way in,” Kidman says. “That was my warmup, always. It's one of the hardest, but it's so good and it's so fun to do."

She found Ball’s offscreen voice and mannerisms with the help of old recordings Ball and Arnaz's daughter, Lucie Arnaz, supplied of them talking to their kids, as well as footage of Ball directing scenes while smoking a cigarette.

"It was so helpful," says Kidman, who also watched "a number of different interviews (of Ball). She had very specific hand gestures. She would emphasize a lot of things with her hands, and they were very direct and very precise."

Kidman and Bardem are both extremely grateful to the younger Arnaz, who was hands-on yet kept her distance throughout shooting.

"If I had any doubt or problem, I could call her and she would let me know, but I didn't do that too often," Bardem says. "If I opened that door, it would've distracted me from the purpose of (this film) is, which is the story that was written."

"She (told) us things that were extremely private," Kidman adds. "We're playing her parents, so the idea of protecting her is important."

This article originally appeared on USA TODAY: 'Being the Ricardos': Nicole Kidman's kids judged her Lucille Ball