NEW YORK — It's practically become a rite of passage for teen pop stars — if 你 want to 交叉, 十字架 over to the big screen, it might help to channel a little Joan Jett. That's what Britney Spears did in "Crossroads," when she sang along to "I 爱情 Rock 'N Roll," and now JoJo follows suit, in her upcoming film debut, "R.V."

"I made a conscious decision not to play a singer in a movie, so I'm definitely not [singing for real]," she said. "But in one of the scenes, I have to put on an iPod and just sing very off-key to a song I had no idea existed before, a song 由 Joan Jett. It's so out of character...