Kristen Stewart and Dakota Fanning have been winning praise for their turns as real-life teen rockers in "The Runaways" since the film premiered at the Sundance Film Festival in January. An early viewing had MTV News declaring that KStew, in the role of Joan Jett, "curses and growls as the part demands," while feting Fanning for a "riveting portrayal" of Cherie Currie.

Going into the June '09 shoot, though, both actresses were beset with anxieties that go along with portraying iconic musicians, both of whom would be on set each day. "I think playing a real person that was going to be there," Fanning told MTV News, ticking off a list of her fears. "Also, singing, for me, which was very intimidating. I didn't really know exactly who the Runaways were, so just learning about them and watching the 'Live in Japan' of 'Cherry Bomb' and realizing I had to do that was a little scary. But that's kind of what drew me to it and excited me."

Indeed, as Stewart explained, such fears are part and parcel of working in front of the camera. "I don't remember the last time I wasn't really freaked out before I started a movie," she said. "And the second you sort of get into the groove, you find it. It becomes what you thought it would be when you read it. You have to have that second [of fear], or else you're probably not doing something very worthwhile."

And the only way to overcome these worries is to get on with the show. "After you get the first day under your belt, you feel pretty good about it," said Fanning.

They may have felt good about it after that first day, but the rest of the shoot didn't get any easier. "Every day was a huge scene," said Stewart. "There was never one day that was just like, 'Oh yeah, no big deal today.' Every day was loaded."

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

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