Fox announced today that red hot singers Katy Perry and Avril Lavigne would be appearing as guest judges on the upcoming season of American Idol. They will be joining a roster of guests this year that also includes Victoria Beckham, Mary J. Blige, Kristin Chenoweth, Neil Patrick Harris, Joe Jonas, and Shania Twain. Here is the official press release:

Katy Perry and Avril Lavigne will join American Idol as guest judges during the final two days of auditions held this week in Los Angeles. On their respective days, Perry and Lavigne will sit at the judges' table next to Simon Cowell, Randy Jackson and Kara DioGuardi while the final group of singing hopefuls tries for a "Golden Ticket" to Hollywood. Recently, Victoria Beckham served as a guest judge in Denver and Boston, Mary J. Blige shared her expertise in Atlanta, Joe Jonas and Neil Patrick Harris guest-judged in Dallas, Kristin Chenoweth joined the panel in Orlando and Shania Twain sat at the judges' table in Chicago.

American Idol returns for its ninth season in January 2010 on FOX.

Since the 2007 digital release of the hilarious, zeitgeist-capturing single "Ur So Gay," singer-songwriter Katy Perry has gone from Internet music sensation to bona fide star. Her multi-platinum debut album, "One of the Boys," generated four hit singles - "I Kissed A Girl," "Hot N Cold," "Thinking Of You" and "Waking Up In Vegas" - three of which reached No. 1 on the Billboard charts. The Grammy-nominated artist has captured the hearts of critics and audiences alike. Perry, who was awarded Best New Act at the MTV Europe Music Awards and voted Best New Artist by readers of Rolling Stone, finishes her sold-out "Hello Katy" worldwide tour in September.

Avril Lavigne released her debut album, "Let Go," when she was 17 years old. The album, which has sold more than 16 million copies worldwide, snagged eight Grammy Award nominations and four Juno Awards. With three albums released to date, Lavigne has sold over 30 million albums worldwide. She is currently in the studio working on her fourth album. In addition, Lavigne designs her own line of clothing, Abby Dawn, and she just launched her first fragrance, Black Star.

American Idol is created and executive-produced by Simon Fuller, founder of 19 Entertainment; and executive-produced by Cecile Frot-Coutaz, CEO, FremantleMedia North America; and Ken Warwick, executive producer, FremantleMedia North America.