Mason Thames First Met Mckenna Grace in an Uber, They ‘Clicked Immediately’ (Exclusive)

Mason Thames and Mckenna Grace had an instant connection.

The former child stars, who are both stepping into romantic roles in the Colleen Hoover adaptation Regretting You, first crossed paths months before they got to set — and they “clicked immediately,” according to Thames.

While discussing Regretting You alongside Grace, 19, the Black Phone star, 18, tells PEOPLE he did not have to work hard to get sparks flying between their characters Clara Grant and Miller Adams since “chemistry with Mckenna was so easy.”

“From the moment I met her, we were in this Uber going to see, I think, Deadpool & Wolverine,” he recalls. “And instead of it just being super, super-duper awkward for a first meeting, it was so funny and so awesome.”

“We just clicked immediately,” adds Thames. “And ever since then, we just hung out all the time.”

Grace and Thames’ connection lights up the screen in Regretting You, and it hasn’t gone unnoticed off-screen, either. The pair were photographed holding hands in June, and sparked romance rumors after posting videos of them kissing on TikTok.

There were a lot more smooches where that came from, as Thames says he and his costar improvised “a lot of kisses” for the cameras — which “didn’t always make it” in the final cut of the Josh Boone-directed film.

During one moment in a “prom-posal” scene, the two actors felt that their characters would smooch, “and so we did — like, every take,” Thames says, recalling that there was “maybe one take where we didn’t do it.”

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“That’s the best part,” Grace chimes in, laughing. “We’re watching the movie. And we did that and it didn’t make it!” Evidently, Boone decided to “cut it out” of the scene, the actress says, leading her to wonder: “Why didn’t he just tell us on set?”

Beyond Regretting You, Grace and Thames are uniting onscreen in another forthcoming film, New Year’s Rev. The pair filmed the comedy about and produced by Green Day — which premiered at the 2025 Toronto International Film Festival — back to back with the romantic flick. They also learned they would be starring together in the projects at the same time, they say.

“I was working on How To Train Your Dragon and I got Regretting You. Also right before that I signed on to this Green Day movie and then I signed onto Regretting You,” Thames recalls, adding that he immediately sent his future costar a message that read, “Hey, like so excited.”

Thames continues, “I was like, ‘So excited to work with you.’ And she was like, ‘Oh yeah, I’m so excited for Green Day.’ I was like, ‘What? What do you mean Green Day? I’m talking about Regretting You.’ She’s like, ‘What do you mean Regretting You?’ So we found out we were doing two movies back to back, which is so crazy.”

“But also finding out about those seven months in advance, eight months in advance is also crazy,” Grace says. Thanks to the advance notice, she adds, the pair had “all of that time to just hang out and mess around and just be stupid.”

“So we were very excited to finally get on set,” she adds.

The costars have also spent time together after they wrapped filming in spring. In August, Thames told PEOPLE that Grace was by his side as he rang in his birthday earlier this summer. “I was home back in Texas and I got a little birthday week,” he said at the time, “and Mckenna was also there, and that was really nice.”

Regretting You, based on Hoover’s 2019 novel, also stars Allison Williams, Dave Franco, Scott Eastwood and Willa Fitzgerald. Williams stars as Morgan Grant, a young mom who puts her ambitions on hold to raise her teenage daughter, Clara (Grace). But when a family tragedy puts more strain on their already complicated relationship, they must figure out how to navigate life together.

Regretting You is in theaters Oct. 24.