'Red One' is an action-comedy that can 'smack you down with heart,' Lucy Liu says

Lucy Liu didn’t know that she would have to do stunts when she signed on for Red One, an action-adventure Christmas comedy that follows an unlikely duo played by Dwayne Johnson and Chris Evans, who team up to locate a kidnapped Santa (J.K. Simmons).

“I was actually really relieved … that I could just cruise in there and just be the boss lady. No big deal!” she told Yahoo Entertainment. “But when I got there, they said, ‘We’re going to have the stunt coordinator show you what the moment’s going to be when the action starts’ … and I was like, ‘Wait a minute!’”

The actress, best known for her action-packed roles in Kill Bill and Charlie’s Angels, plays the no-nonsense head of the Mythological Oversight and Restoration Authority in Red One. Its director, Jake Kasdan, initially said she might have to do “maybe a punch or a kick,” but it turned out to be “a whole big stunt scene.”

“There was a lot more of a stunt scene than what was [shown] in the movie, but we got trained… really quickly,” she said. “I love and I’m thrilled by doing stunts. … I love women doing stunts in general!”

Liu also gave props to her co-star Kieran Shipka for kicking Chris Evans and Dwayne Johnson into shape.

“Had to do it to 'em,” Shipka joked.

Red One is also the first of Liu’s movies that she felt her 9-year-old son, Rockwell, could watch.

“I don’t think a lot of the movies I’ve done in the past are appropriate for him," Liu said. "I thought, ‘This one has a bit of scary creatures, maybe it’s not going to be right for him,’ but he loved it.”

After bringing her son to the premiere, Liu saw a video of Rockwell saying how proud he was of her.

“That blew my heart up completely,” she said. “You want your kids to be happy … and to know that he feels pride for me makes me feel the greatest joy.”

Red One also marks a milestone for Shipka. Her turn as the shape-shifting witch who kidnaps Santa is her first onscreen role as a villain.

“I created a backstory that made sense for her in my brain, and by the time I put on the wig and the makeup, I kind of went to the dark side,” she told Yahoo Entertainment. “She genuinely thinks she’s doing the right thing, so I just transported myself into that mindset and tossed away my judgment.”

Shipka has had a busy year — she had memorable parts in the box-office hits Longlegs and Twisters.

“This is year 18 or 19 in the biz, and I had so much fun the past couple of years, making a variety of films, even though I didn’t seek out these different genres,” she said. “I feel more excited than ever to just do what I do.”

Both actresses said they were excited to be a part of a movie that was so different from standard holiday fare while paying homage to the thrill of saving Christmas.

“There’s so much folklore … it’s a very original concept,” Shipka said. “It’s also action and comedy, but at the end of the day, it has a real kind of heart.”

Liu said she loved that it’s a combination of an “action buddy movie” with the fun premise of saving Christmas, but at the end, “they smack you down with heart.”

Red One is in theaters now.