"CSI" Star Marg Helgenberger was recently interviewed for French radio and was asked what she thought of previous co-star Justin Bieber.  And it looks like Bieber's taste for practical jokes didn't impress anyone.

"Justin Bieber wasn't bad.  He had never acted before. I shouldn't be saying this, but he's kind of a brat. He was actually very nice to me, but he locked one of the producers in the closet. And he put his fist through a cake that was on the table."

Well, to a Bieber, thems fightin' words!  Justin got on Twitter today to fire a shot back,

"It's kinda lame when someone you met briefly and never worked with comments on you.  I will continue to wish them luck and be kind."

“I know who i am and sometimes people r just going 2 say what they want. Keep ur head up and be the man ur mama raised.”

“There is ALWAYS Gunna Be People Telling you can’t do something, There’s always gunna be haters, Just Keep Smiling.”

Never thought I'd see the day where we'd have a war of the words between a 17-year-old singer and a 52-year-old actress.