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.

Both Perry and Lavigne will join the judging panel on different days to critique the Los Angeles hopefuls as they audition for a "Golden Ticket" to American Idol's Hollywood Week round.

Perry and Lavigne will be the final two audition guest judges to fill-in for Paula Abdul -- who last month used her Twitter page to announce that she would not be returning as a judge for Idol's ninth season.

While Idol will not begin its semifinal performance shows until late February, a series of guest judges have replaced Abdul at the ninth-season callback auditions.

Victoria Beckham (Denver and Boston), Mary J. Blige (Atlanta), Joe Jonas and Neil Patrick Harris (Dallas), Kristin Chenoweth (Orlando), and Shania Twain (Chicago) have served as guest judges at the ninth season's previous audition locations.

Fox had announced Beckham and Perry's Idol participation shortly after Abdul's departure announcement, however Perry's audition city had not been confirmed until now.