Rihanna entertained the cast and crew on her new film by pretending to be a "stoned valley girl".

The songstress stars alongside the veteran action star in the Peter Berg-directed Battleship. Filmmaker Peter says Rihanna was a hilarious cast-member and provided many great moments during shooting sometimes at the expense of her co-stars.

"Rihanna is an artist and she works her ass off. I put her through [the ringer]. She came in for her first meeting and I told her to just come in and be herself with no glam. She was in a pair of jeans, a T-shirt, no make-up and a pair of flip-flops, and for two hours, we just played. She improvised," he told Collider.com.

"She read Liam Neeson's role. She has voices that she can do, that she plays around with, with her friends. She does a really dumb, stoned valley girl who's really funny. I had her read Liam Neeson's role like a stoned valley girl, and it was hilarious.

"What it showed was a desire to not take herself too seriously and to not be afraid to be stupid, which is half of being good at acting. You have to be willing to take a chance."

Peter thinks Rihanna can make the difficult shift from singer to respected actor. He was impressed with her talent.

"There's a long, long list of musicians who have become successful actors. Frank Sinatra in From Here to Eternity was my first recollection of it. I thought The Bodyguard with Whitney Houston was a great film. Mariah Carey blew my mind in Precious," he explained.

"If you look at Rihanna's videos, she's obviously incredibly sexy, she's very intense, and she's really hot. If it was that easy to do that, there would be thousands of Rihannas. If you've never been on a video set, there's nothing glamorous or sexy about it. That all comes from her. She's a performer, and she does a great job in Battleship."