Mason Thames and Mckenna Grace Improvised Kisses in ‘Regretting You’ (Exclusive)

Things got spicy on the set of Mason Thames and Mckenna Grace’s new movie.

Speaking to PEOPLE about Regretting You, the costars admit they improvised “a lot of kisses,” as Thames, 18, puts it. In fact, he says, those improvisations “didn’t always make it” into the film. 

For one scene involving a prom-posal in the Colleen Hoover adaptation, directed by Josh Boone, the two actors felt that their lovestruck characters Clara and Miller would smooch. “And so we did — like, every take,” says Thames, recalling that there was “maybe one take where we didn’t do it.”

“That’s the best part,” says Grace, 19, laughing. “We’re watching the movie. And we did that and it didn’t make it!”

Evidently, Boone “cut it out,” adds the Ghostbusters actress. “Why didn’t he just tell us on set?”

Regretting You, costarring Allison Williams and Dave Franco, follows Grace’s Clara mourning the loss of her father (Scott Eastwood) and aunt (Willa Fitzgerald). While dealing with complicated family grief, she and Thames’ Miller hit it off. 

While it seems Grace and Thames have hit it off too — they were photographed holding hands in June, and sparked romance rumors after posting videos of them kissing on TikTok — they only hint at their shared connection in conversation with PEOPLE.

“Chemistry? I hardly know her!” jokes Grace when asked about her onscreen rapport with Thames. The How to Train Your Dragon actor, meanwhile, calls their chemistry “so easy,” recalling meeting the actress-musician in an Uber. “Instead of it just being super-duper awkward for a first meeting, it was so funny and so awesome. We just clicked immediately. And ever since then we’ve just hung out all the time.”

Coincidentally, the two costars worked in back-to-back projects, they confirm: following the release of Regretting You, they’ll appear in New Year’s Rev, a comedy about and produced by Green Day that premiered at the 2025 Toronto International Film Festival. 

Thames told PEOPLE in August that he rang in his 18th birthday this summer with family and friends by his side, including Grace. “I was home back in Texas and I got a little birthday week, and Mckenna was also there, and that was really nice,” he shared at the time. 

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Regretting You is in theaters Oct. 24.