Kristen Stewart might be doing some onscreen shocking in 'The Runaways' with her girl-on-girl kiss and her portrayal of rock and roll life.

But while filming 'New Moon,' she did her real shocking off-camera.

As 'New Moon' rocked the film world with its celebrated DVD release this weekend, director Chris Weitz tells PopEater exclusively that if there were a blooper reel for swears, the actress playing earnest Bella Swan would dominate.

"It's Kristen by several lengths actually," says Weitz of his champion swearer. When asked what the swear of choice was for Stewart, he laughed. "I couldn't say over a domestic phone line."