Greta Gerwig Reveals She 'Stood in the Back' of “Barbie” Screenings to See Audience's Reaction

The director said she wanted to find out for herself what people thought of the movie

Greta Gerwig is spilling a surprising secret about her blockbuster movie, Barbie.

The director, 40, revealed that she decided to do her own covert field research during the film's opening weekend in July by hiding in the back of the theater during screenings in order to see the audience's reaction firsthand.

“I went around to different theaters and sort of stood in the back, and would then also turn up the volume if I felt it wasn’t playing at the perfect level,” she recounted during a screen talk on Sunday at the BFI London Film Festival, according to The Hollywood Reporter.

She said at one of those sneaky screenings, she heard a woman cracking up over a particularly zingy one-liner about the Proust Barbie. “And I was like, ‘That joke was for you!' ” Gerwig told the festival audience.

Gerwig went on to share that the film was "the most joyful" experience she's ever had on a set. “So, I thought, if I can make a movie that is half as fun to watch as it was to make, I think maybe we’ve got a shot," she said.

Related: Greta Gerwig and 'Barbie' Cast Go Behind the Scenes of Film's Costumes in New Clip (Exclusive)

Gerwig also admitted that she sometimes dealt with self-doubt about the script and some of her creative choices, including the much-loved "I'm Just Ken" dance scene, which depicts the numerous Kens fighting.

“That sequence, in particular, was just filled with choices that thrilled me and made me so happy, but then I’d be driving home at the end of the day and thinking, 'Oh no!' ” she recalled.

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While she continues to bask in Barbie's history-making success, Gerwig is also turning her attention to new creative endeavors. She teased that she is working on something new at the moment, but didn't share any details.

“I’m in the writing process,” she said at the festival, adding that she is still grappling with self-doubt. "It’s hard because I’m having recurring nightmares.”

Related: Greta Gerwig Is ‘Terrified’ to Direct Upcoming ‘Narnia’ Movies: ‘It's Extraordinary’

In July, Gerwig echoed that same sentiment when talking about another upcoming project that will see her directing two Narnia movies, based on acclaimed British author C.S. Lewis' classic The Chronicles of Narnia book series.

“I haven't even really started wrapping my arms around it. But I'm properly scared of it, which feels like a good place to start. I think when I'm scared, it's always a good sign,” she said on the Inside Total Film podcast.

“Maybe when I stop being scared, it'll be like, 'Okay. Maybe I shouldn't do that one.' No, I'm terrified of it. It's extraordinary. And so we'll see,” Gerwig continued.

“I hope to make all different kinds of movies in the course of the time I get to make movies, which — it's a long time, but it's also limited," she added. "I want to do big things and small things and everywhere in between, and having another big canvas is exciting and also daunting."

Sometime in the future, Gerwig also hopes to dive into the Barbie universe again and bring fans even more movies.

"There’s a tone and a humor and a joy, and obviously the world is so beautiful," she told PEOPLE in July, declaring, "I want to go back to Barbie Land."

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