While at their Netflix film's premiere in Los Angeles last week, Kutcher wore a serious expression and kept his hands in his pockets while standing next to a smiling Witherspoon — something the 45-year-old revealed Wednesday was on purpose.
"Here's the thing: If I put my arm around her, and was like all friendly with her, I'd be having an affair with her," Kutcher explained during a guest spot on the Chicks in the Office podcast. "Like, the rumor would be that I'm having an affair with her."
Rob Latour/Shutterstock Reese Witherspoon and Ashton Kutcher
During a Friday appearance on Today, the Morning Show star said she got an email from Kunis, 39, whom she calls a friend. "She even emailed us last night," she said the day after the premiere. "She goes, 'You guys look so awkward on the red carpet together.' "
Addressing working with Kutcher, Witherspoon added, "It's just fun 'cause when you know a girlfriend so much, it was just fun to get to know her significant other 'cause I've loved her for so long."
Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human-interest stories.
Steve Granitz/FilmMagic; Axelle/Bauer-Griffin/FilmMagic Mila Kunis; Reese Witherspoon and Ashton Kutcher
Of anticipating working with Witherspoon, Kutcher said on Chicks in the Office, "I was scared — like, I was intimidated by her. I was like, 'Man, I can't believe Reese Witherspoon is sending me video messages.' "
The Iowa-born actor, wearing a "Dad" baseball cap (he and Kunis share two kids: daughter Wyatt, 8, and son Dimitri, 6), said that Witherspoon is the one who pulled him back into the world of rom-coms "after a decade."
"She's such a badass," the Punk'd alum said. "She has such a presence ... she has so much range, she can do drama, she can do comedy, she can do everything. She's such a movie star."
Witherspoon and Kutcher lead the cast of the romantic comedy as Debbie and Peter, "best friends and total opposites" who learn a valuable life lesson from a little change of scenery.
"She craves routine with her son in L.A.; he thrives on change in N.Y.," reads an official logline. "When they swap houses and lives for a week, they discover what they think they want might not be what they really need."
Speaking with PEOPLE about Your Place or Mine in December 2022, Kutcher said signing up for the film was an "easy" decision, as he "finally got the opportunity" to collaborate with Witherspoon and McKenna, 55, "two women I have wanted to work with for years."
The film is co-produced by McKenna, Jason Bateman, Michael Costigan, Lauren Neustadter and Witherspoon, the latter of whom Kutcher said working with "is like hanging out with a best friend."
"We just had fun!" he raved of their time on set. "I can talk to Reese about anything — acting, business, kids, media, football. She's always game."
And Witherspoon couldn't have agreed more, telling PEOPLE of Kutcher, "I think he's so funny. We have a very similar sense of humor and timing."
Your Place or Mine is streaming Friday on Netflix.