Scott Caan and Elizabeth Debicki have joined the cast of the new 'Once Upon A Time In Hollywood' movie.

The pair will join Brad Pitt in David Fincher's follow-up to Quentin Tarantino's 2019 film, which starred Pitt and Leonardo DiCaprio.

According to The Hollywood Reporter, it is unclear who Caan and Debicki will play in the upcoming movie.

The story is said to feature two key female roles, "one who runs a bar and mud wrestling establishment and one a trophy wife" but it has not been revealed if Debicki will play once of these or an entirely new part.

It will be a reunion for Pitt and Caan, who previously worked together on the 'Ocean's' movie series.

Brad, 61, will reprise his role as stuntman Cliff Booth, in the upcoming film, which Fincher will direct for Netflix from a Tarantino script.

It's said that Tarantino retains the rights to the characters in 'Once Upon A Time In Hollywood', while Sony - which financed and released the movie - retains the film itself, which is why the upcoming project is not seen as a sequel or prequel despite using the Booth character.

It's unclear if Leonardo DiCaprio will return as Western TV star Rick Dalton.

Tarantino won't be at the helm, which means the film won't count as his 10th and final film.

The director had had been set to reunite with Pitt - who also appeared in 'Inglourious Basterds in 2009 - for third collaboration on 'The Movie Critic.

According to Deadline, Tarantino has "simply changed his mind" after delaying production to rewrite the script.

Now, he's expected to go back to the drawing board in a bid to find a firm idea for what will be his final film.