Margot Robbie was 'positively gleeful' watching Colin Farrell sing and dance in new movie

Colin Farrell was never much of a theater kid.

“I was too busy kicking a football around until my mid-teens,” says the Irish actor, who is the son of professional footballer Eamon Farrell. But in new movie “A Big Bold Beautiful Journey” (in theaters Sept. 19), Farrell gets a chance to flex his pipes as David, who goes on a surreal odyssey through his memories with the defiantly single Sarah (Margot Robbie), whom he meets at a wedding.

In one memorable sequence, David is whisked back to his 15-year-old self in high school, where he’s the star of the musical “How to Succeed in Business Without Really Trying.” The “In Bruges” star croons and soft-shoes alongside a teenage cast, before he and Robbie lead the entire audience in a sing-along of “Been a Long Day.”

“It was so fun,” Robbie recalls. “I was positively gleeful watching Colin do his little jazz hands and jazz feet. It was great.”

“Because you got to observe me squirming for two days,” Farrell quips. “That was the one scene that made me think, ‘I'm not sure if I'm going to do the film.’” All jokes aside, "it was fun, in spite of myself. I did enjoy it somewhat when I got over the initial discomfort of it. The whole theater was full of people. We shot from 2 in the afternoon until 3 in the morning, but the energy was lovely.

“It all felt very alive and very real,” he adds. “So once I got out of my own way, I actually had a good time.”

In the film, Sarah is a lifelong musical theater fan, whose childhood bedroom walls are adorned with posters of “West Side Story” and “Singin’ in the Rain.” Robbie has ample experience singing and dancing in movies such as “Babylon,” “Barbie” and “Amsterdam,” although she downplays her vocal abilities.

“I don't have a singing voice, as you know from anything you've seen me singing,” Robbie cracks. Growing up, "I didn't get to be in the musicals, which is devastating. But like Sarah in this movie, I'm a musical groupie. I would sit there and watch all of the school musicals and just be like, ‘God, I wish I could sing.’ But I did the plays instead.”

To prepare for “A Big Bold Beautiful Journey,” director Kogonada gave Farrell, 49, and Robbie, 35, a long list of viewing “homework,” which included dream-like dramas by Frank Capra and Federico Fellini. The goal, he says, was to embrace the heightened tone and Technicolor artificiality of movie musicals, but without losing the “real human emotions” that fuel David and Sarah’s romantic hang-ups. Both characters struggle to forgive themselves for past mistakes and are reluctant to dive back into relationships.

“Have we grown cynical about the possibility of real connection? And what do we need to confront to have belief in that again?” Kogonada says. “These are two adults who grew up loving musicals and believing in them. How do you retain that romance, but also be honest about the reality of the world?”

Robbie and Farrell remember chatting briefly at events over the years, but never really got to know each other until making “A Big Bold Beautiful Journey.” There was an instant “familiarity that I felt with Margot,” Farrell says, and they bonded over their shared love of nature and food.

“We both eat a lot and get excited about our meals,” Robbie says, turning to Farrell with a grin. “You have an alarming amount of salt on your food, and you never drink water!”

The three-time Oscar nominee says the project was a real “heart-opener,” reaffirming the gratitude and joy she gets from making movies. Farrell echoes her sentiment.

“It’s an incredibly sweet look at what it is to love and let go of the past,” Farrell says. In his day-to-day life, “it all snowballs: film, friendship, parenthood. You can learn about romance through being a parent. You can learn about caregiving through being in a romantic relationship. It all just cascades for me.”