Katy Perry's On "Ooh La La"

Learn something new every day! Katy Perry tells E! News she and “Ooh La La” writer Bonnie McKee snuck in their vocals on the track.

“Me and Bonnie secretly did some background vocals on that song,” Perry said at the premiere in Westwood on Sunday. “So maybe listen for our voices.”

I wonder if Britney even knew that?