Robbie and Pitt star opposite one another in Damien Chazelle’s forthcoming three-hour film.
Chazelle previously directed acclaimed hits including Whiplash and La La Land. Babylon is thought to be another Oscar contender for the filmmaker.
In a recent interview with E! News, Robbie revealed that her kiss with Pitt in the film “wasn’t in the script”.
The actor, 32, said that she improvised the moment with some help from Chazelle.
Robbie said: “I thought, ‘When else am I gonna get the chance to kiss Brad Pitt?’ I’m just going to go for it.”
The Wolf of Wall Street star continued to detail how her conversation with Chazelle went.
Robbie recalled: “I said, ‘Damien, I think Nellie would just go up and kiss Jack. And Damien was like, ‘Well, she could – wait, hold on. You just wanna kiss Brad Pitt.’
“And I was like, ‘Oh, so sue me. This opportunity might never come up again.’ And he was like, ‘It does work for the character,’ and I was like, ‘I think so.’”
After one successful take of the improvised kiss, Chazelle was impressed and asked them to do the scene again.
“He was like, ‘No, do it again. That really works.’ I was like, ‘Oh great,’” said Robbie.
Robbie and Pitt have starred together in Quentin Tarantino’s Once Upon a Time… in Hollywood (2019), as well as in Adam McKay’s 2015 film The Big Short.
The Australian actor went on to reveal that she also kissed her co-star Katherine [Waterston] for the film, but was unsure whether that scene made the final cut.
In Babylon, Robbie stars as an up-and-coming actor Nellie LaRay. The film is set in1920s Hollywood as the movie industry transitions out of the era of silent films. Pitt plays actor Jack Conrad.
Robbie has previously said that she had never worked as hard on a film as she did on Babylon.
“I’ve never worked that hard in my life,” she said. “[I was] shattered by the end of that job.”
Babylon will be released in cinemas on 23 December.