J.K. Simmons and Nina Arianda have joined the cast of 'Being the Ricardos'.

The 66-year-old actor and 36-year-old actress have been tapped to star as William Frawley and Vivian Vance in Amazon's new movie about the 1950s sitcom 'I Love Lucy'.

The duo will star alongside Nicole Kidman and Javier Bardem, who are in final negotiations to play stars Lucille Ball and her real-life husband Desi Arnaz.

Simmons' character, Frawley, played neighbour Fred Mertz in the show while Arianda's alter-ego, Vance, portrayed Fred's wife and Lucy's best friend Ethel Mertz.

Aaron Sorkin is writing and directing the flick, which is set during one production week of 'I Love Lucy' – from a Monday table read through to audience filming on Friday – as Lucille and Desi face a crisis that could end their careers and another that could end their marriage.

Nicole's casting as Lucille has divided fans with some suggesting the likes of Debra Messing or Carole Cook would have been better suited for the part but the star has vowed to "try (her) best" in the role.

The 53-year-old actress said: "I was like, ‘Yeah, I would love to give it a go.' With Aaron’s words and his direction and Javier … that’s kind of a wonderful prospect to, you know.

"But yikes, off we go. Give it a go. Try my best—see if I can do it."

'The Undoing' star revealed that she has been watching episodes of 'I Love Lucy' to prepare for the film.

Nicole explained: "I love Lucille, having looked now and delved into her.

"She's an amazing woman. I'm very excited for people to see what Aaron found out about her and the way he's interpreted Desi and Lucy and the way that it's so rich. I didn't know any of this."