ET was with Kate Hudson Monday night as she premiered her new movie, 'My Best Friend's Girl,' in Hollywood. Watch our video of Great Kate and her co-stars, Dane Cook and Jason Biggs as they hit the red carpet.  Kate tells ET about the new film and about watching her language in front of her adorable son, Ryder. "I try very hard not to do it around my son," Kate says about using "bad" words. "That's a big no-no. You drop something, you say a bad word, and they're like, 'Mommy, you don't say that!'" 'My Best Friend's Girl,' which hits theaters this Friday, September 19, tells the story of a guy (Cook) whose best friend (Biggs) asks him to take his ex (Hudson) on a date to treat her so badly that it convinces her of what she's missing -- but does the plan backfire? "30 Rock"'s Alec Baldwin co-stars as Dane's single, on-the-prowl dad.