In a new interview, rocker Joan Jett discusses Kristen and her role as the famous rocker in ‘The Runaways’. I’ve included only the Kristen related parts below.

And the icon checklist doesn’t stop there. Not when they are making a movie based on your early career (The Runaways due in 2010 ) with one of the hottest young actresses in Hollywood (Kristen Stewart) cast as you. And then, just to drive the point home, a Joan Jett Barbie Doll has been released this year in time for Christmas.
It’s a long way from the late ’70s when Jett first appeared on the punk scene with the Runaways, a band that while successful overseas, never gained more than a cult following in the U.S.
Still, Jett has embraced the film, which is based on lead singer Cherie Currie’s 1989 autobiography Neon Angels. Currie’s role is played by Dakota Fanning. As an executive producer, Jett has worked closely with Stewart to recreate, well, herself.
“It’s been pretty surreal,” she says. “First of all, she cut her hair and that certainly helped my vision of it. She wasn’t wearing a wig. She was actually living in the hair and I would hope that it helped her a little bit to embody it.”
“I thought that just in general our energy, the way we handle day-to-day things, plus our physical movements in space, were very similar. A lot of kind of fidgeting, a lot of playing with the hair — a lot of that stuff sort of came natural. But for a lot of the physical aspects, she watched me a lot, so it was surreal, but in a nice way. It wasn’t uncomfortable and it wasn’t creepy.”
Though Stewart’s portrayal of Jett has been gaining a lot of attention, Jett is quick to point out that the film is about the group, not her.

“I have to really stress that this is not a biopic,” Jett says. “It sort of goes over how the band started, but you can’t take each aspect as a fact. The way I look at it this movie is based on Cherie’s book and I see it as basically a parallel narrative … so I’m not ever going to able to judge it as a true Runaways story. Because that’s not really what this is. To me, it’s more of the story of two girls and how they deal with this event in their life called The Runaways.”

source