Katy Perry

Katy Perry and Britney Spears collaborated on “Ooh La La!” track for the “Smurfs 2” movie.

Written by Bonnie McKee, the song plays over the end credits of the movie.

According to E! News, Katy has revealed at the Los Angeles premiere of the film, that cinemagoers will hear something a little bit different than usual.

"Me and Bonnie secretly did some background vocals on that song. So maybe listen for our voices," she said. Both singers wore blue at the premiere and didn’t meet until the Hollywood event. Katy took her grandmother to the event, while Britney was accompanied by her two sons, Jaden and Sean.

Meanwhile the “Toxic” singer, Britney Spears, is working on her eighth studio album with Black Eyed Peas producer, will.i.am. The 31-year-old diva gushed last month that she was continually experimenting and that she hoped people will be "surprised" by the new musical approach.