American Idol Avril Lavigne joining Katy Perry as 'American Idol' audition guest judge 09/02/2009 Fox has announced singers Katy Perry and Avril Lavigne will serve as guest judges during American Idol's ninth-season auditions in Los Angeles this week. Read More RELATED NEWS Kelly Clarkson reunites original 'American Idol' judges Simon Cowell, Paula Abdul and Randy Jackson'American Idol' was "one of the worst decisions I've ever made," says former judge Ellen DeGeneresCrystal Bowersox and husband Brian Walker announce divorce TAGS: American Idol Paula Abdul Kristin Chenoweth Katy Perry Mary J. Blige Joe Jonas Neil Patrick Harris Avril Lavigne Victoria Beckham Shania Twain
