KATY Perry wants to be an honest judge on American Idol. The singer is planning to imitate Simon Cowells brand of tough love when she appears as a guest judge on American Idol later this month. The 24-year-old star said: I might become a little bit of a buddy with Simon, hes a very truthful and honest. Im not there to build them up. Its weird, because I dont want to break their hearts, but everyone knows someone whos been doing karaoke and doing little gigs here and there, and nobody has told them that they cant sing on pitch for, like, 15 years? And youre like, 'Someone needs to say something. And, unfortunately, I might be that gal, to tell you the truth. I always have been. Katy is not the only celebrity to fill Paula Abduls vacant chair on the shows judging panel. Shania Twain and Victoria Beckham have also made one-off appearances. Expo