Alana Haim says fans of her music will be "pretty shocked" to see her star in her debut feature film Licorice Pizza.
The singer and musician said she had "no idea" how to read the script sent to her by director Paul Thomas Anderson, but was "so excited" by the project.
The 30-year-old stars alongside Bradley Cooper and Sean Penn in the coming-of-age comedy-drama, which is scheduled for release on New Year's Day.
"I was just so excited that Paul was sending me a script. I was actually in London when I got the script, and I didn't know it was coming," she told the PA news agency.
"I opened my email, and there was this untitled Word document that I opened, and it was the first script I had ever read in my life.
"I mean, me and my sisters don't get sent scripts - like, we're musicians. There's an art to reading a script, I had no idea what I was doing."
Haim, who performs alongside her two sisters Este and Danielle, said the script's scenes "jumped off the page" and she "couldn't put it down".
She said several scenes from the film were based on her own life, and that it was "funny seeing it now".
On her fans' reaction, she said: "I'm just as shocked with them. I think they'll be very shocked because I've never done this before, and me and my siblings, we've done little things, we love making funny videos, me and my siblings love making people laugh and making funny videos, but nothing to an extent of a movie.
"So maybe they won't be so shocked, but pretty shocked. It's a major motion picture, and I'm still shocked that Paul saw something in me that he thought he knew that I can do this role and do Alana.
"It's gonna be pretty shocking. My parents were the most shocked. My parents didn't believe it. And if my parents can't believe it then literally no-one can believe it."
