Gwen Stefani is such a big star, it sometimes seems like everything comes to her easily.

But no — she said breaking into film was just as daunting a process as making her solo album, despite an initial lucky break that helped her catch the eye of director Martin Scorsese.

"Marty's daughter loves No Doubt," Stefani said. "So when he saw my picture from the Teen Vogue cover, like on the side of a bus stop, he said to her, 'Who's that girl? We should get her to try out!' " (see "Gwen Stefani Feeling Hella Good About Role In Scorsese Flick").

This, of course, came five months after Stefani had first expressed interest in being in the director's upcoming Howard Hughes biopic, "The Aviator." The singer's agent had cautioned her not to get too excited about it, but once Scorsese was expressing interest back, Stefani thought she had a real shot at landing the part of Jean Harlow, who starred in Hughes' 1930 aviation melodrama "Hell's Angels." Then came the call to come audition. "My stomach was on the floor," Stefani said. "It's totally humiliating to walk in and have to try out. They know who you are, but it's a casting-call thing."

Stefani tried to calm her nerves by telling herself that it was just a small part, so small that she couldn't even find it in the script. "But let's face it, there's never a small part in a Martin Scorsese film," she said. The people running the casting call also tried to ease Stefani into the process, giving her advice about how to act and dress. "They told me, 'Don't dress like a rock star, you have to dress up nice,' " she said. "They couldn't have been more helpful and wanting me to get it. These casting girls let me do it a million times, but I left there with sweat."

Then came the callback. Stefani auditioned again, this time in front of the film's star, Leonardo DiCaprio, as well as Scorsese himself, which was even more nerve-racking, she said, because she could hear the other actresses trying out in the other room. "It was really awkward," she said. "And all these other girls were coming out of there going, 'Oh, God!' "

Despite her fears, Stefani nailed the part. Noting the parallel in her situation and that of her character — "[Scorsese] gave me my first role in a major film, Howard Hughes gave Jean Harlow her first big lead role" — she sent Scorsese flowers with a note echoing her one line, swapping Scorsese's name for Hughes, of course: "I would like to use this occasion to publicly thank Mr. Scorsese for the opportunity he gave me. Thank you."

It's been a year since Stefani shot her part for "The Aviator," due December 17, and while playing Harlow was a dream come true for the singer, it only made her all the more eager to get another chance at being on the big screen.

"Obviously, [Harlow's] the original blond bombshell," Stefani said. "You can see that she inspired me. And [the part] was really familiar, walking down the red carpet, so it wasn't really branching out. Acting is a lot different than singing. It's not as theatrical, it's a lot more subtle, and that's a lot harder. Simpler is usually harder. So I would love to do more. I got my feet wet, but I would love to go swimming."

Check out everything we've got on "The Aviator."

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