"I was overwhelmed and a little intimidated when I first came on to this project," the actress tells ET.
The 23-year-old actress stars opposite Pitt in the high-octane action comedy Bullet Train, directed by David Leitch, about five assassins aboard the same bullet train out of Tokyo. While working with an icon left her feeling jittery about her first day, King says she was most surprised to find out how "amazingly normal" Pitt is in real life.
"I was overwhelmed and a little intimidated when I first came on to this project," King tells ET's Nischelle Turner at the film's Los Angeles premiere on Monday night. "It's just like, 'Holy cannoli, an action film with David Leitch and Brad Pitt,' like, 'This is wild!' And you get on that set, and it just feels so comfortable and exciting and, you know, you can take risks."
In spite of her initial nerves about working with Pitt, King credits the 58-year-old actor with being a big part of the relaxed environment on set.
"We've got Brad who, you know, just kinda sets the tone," she says. "I mean, he's an amazing, talented leader."
The tightknit cast also includes Aaron Taylor-Johnson, Brian Tyree Henry, Bad Bunny, Sandra Bullock, Michael Shannon and more.
"Brad is such a big cheerleader for everybody," she continues. "It’s just really it was wild to be like, 'Wow, what a nice, freaking normal guy."
The cast camaraderie has been on full display throughout their recent press tour.
"We just have the most wonderful friendship and I’m so grateful for it because there’s nothing better than loving a project you're doing and also being proud of the outcome of what you guys did together," she says.
In fact, they're more than just a band of actors -- King jokes that they actually formed a real band, adding, "We have a whole band name and everything!"
According to King, "We're called Naked Below the Line." Although she's not entirely sure where the somewhat NSFW moniker came from. "I don't even remember the story behind the band name!"
"I don't know how it happened! We just have the most wonderful time together," she adds.
Bullet Train speeds into theaters on August. 5.