"American Idol" has been a launching pad for many talented young singers, and that's partly thanks to the "American Idol" guest judges. The judging dynamic was ruptured when Paula Abdul decided to leave the panel, so the producers decided to fill the void by featuring different guest judges throughout the audition process. Many judges tried and failed, others hit a home-run. Here's a list of the five best "American Idol" guest judges.

  1. Katy Perry.  Katy is hot, hot, hot right now and she brought her A-List magic onto "American Idol" in January 2010. Her honest, hate-free opinion was appreciated by contestants and the audience alike. When she didn't like something, she spoke up. Katy made headlines, however, for calling out fellow judge Kara DioGuardi. Kara wasn't giving feedback on singing performances, instead she was sympathizing with their life situations, and Katy called her on. Her honest bluntness didn't go unnoticed and rumors have been flying that she might replace the infamous Simon Cowell in future seasons.

  2. Mary J. Blige.  Mary might have been a guest judge, but she was right at home on "American Idol". She wasted no time in making her own opinions known, disagreeing with other judges and laughing in contestants faces. Although Blige was a little too audacious to ever replace the sweet Paula Abdul, she certainly made good TV. Blige didn't make it a secret when she was bored, but her unpredictable behavior and hilarious jabs put her at the top for memorable guest performances.

  3. Neil Patrick Harris.  Neil was an instant hit thanks to his magic combination of Abdul's sensitivity and Cowell's bitingly-honest wit. Neil got the job done with subtle humor that made us love him even more than we already did and he showed that he wasn't afraid to stand up to the big dogs. Neil found himself on the receiving end of Stephen Cowell's evil glare more than once, but he didn't even flinch! Hats off to Neil.

  4. Shania Twain.  Shania is not exactly on the tip of everyone's tongue—she hasn't been working in the limelight much since 2005. But once you remembered who she was and what she was famous for, Shania turned out to be pretty endearing. Shania played the role of flirty cougar on the show, and let male contestants know when they had piqued her fancy. Her comments weren't particularly entertaining or insightful, but her vibrant personality and flirtatious comments made her a memorable guest judge to watch.

  5. Victoria Beckham.  Ex-spice girl Victoria proved herself to be smarter than she looks (and sounds.) Posh Spice kept up with the big dogs on the judging panel, inserting helpful and insightful comments from time to time. Unfortunately, and this might be a British thing, she lacked the feminine sensitivity that the judging panel needed. She was fun to watch as a guest, but there is no way Victoria is ever going to be invited on as a permanent feature of the "American Idol" judging panel.

-Armin El-Gazzar