Katy Perry is taking a walk down "Sesame Street" -- <br /><br />The pop princess dons a green metallic dress and a bride's veil for her collaboration with the adorable red puppet, singing a made-for-kids spoof of her hit single "Hot N Cold."<br /><br />In the spoof, the real-life bride-to-be accuses Elmo of changing his mind about whether he wants to play dress-up with her.
