Katy Perry performed her new single 'Firework' on the British TV show 'X-Factor' last night. She performed wearing a firework themed leotard and holding a sparkler. After the performance, the 25 year old American singer-songwriter joked that performing on stage is 'still nerve-wracking' compared to being an X-Factor judge. Katy went on to say that she is still waiting for the call from Simon Cowell, the shows producer.