ABC Radio(NEW YORK) — Kate Mara is set to appear on the big screen in Megan Leavey, which tells the real-life story of former U.S. Marine Megan Leavey and the bond between her and her K-9 partner, Rex, on and off the battlefield.

While there’s an old Hollywood adage that you shouldn’t work with children or animals, Mara found her four-legged co-star to be a pleasure. “Children and animals are super-unpredictable, and I think that’s why people get nervous working with them,” Mara tells ABC Radio.

“But for an actor, if they’re… talented, and constantly bring new things to the table, it’s a complete joy,” Mara continues.  “Anytime I didn’t have a scene with the dog, I was disappointed, because he really kept me on my toes.”

Playing Leavey, however, was intimidating for the actress, who noted, “When you’re playing a Marine, it’s that much more pressure…The real Megan Leavey was super down-to-earth, and easy, and I felt like we’d known each other for years.”

As for Kate’s former gig, House of Cards? While things didn’t end well for her character, Mara found the fan reaction to her character literally getting thrown under a bus to be interesting: “It’s pretty fascinating that the character is still part of the show…It surprises me every time somebody says, you know, they’re still talking about Zoe.”    

Megan Leavey hits theaters Friday.

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