Justin -- Brit's Just a "Madonna Wannabe"

Justin Timberlake didn't keep his stick in a box on Monday night, when he jabbed at ex-galpal Britney Spears at the Rock and Roll Hall of Fame ceremony.

"The world has always been full of Madonna wannabes," said JT as he introduced the Material Mom, an inductee, reports Us. "I might have even dated a couple." Day-um. He also zinged, "She has still found time to kiss someone I may or may not have publicly kissed myself while I was in the audience. Of course you know I was talking about Sean Penn."