As the longest-running American sitcom ever, The Simpsons has been a part of our television lives for what seems like forever. It has become a cultural touchstone and a source of many funny moments over the years, but most of all it has been the coolest medium to see all our favorite celebrities in animated form! We always tune in when we hear about celebrity guests and this coming Sunday's Lady Gaga episode is no exception. Gaga is set to guest-star on the season finale of The Simpsons on May 20th.

All this excitement over Gaga's appearance (and her 18 costume-changes on the show) had us thinking about the other artists who have appeared on the show over the years. Here are your picks for Top 3 artists who rocked The Simpsons:

3. Elton John




On the episode "I'm With Cupid," Elton John made an appearance to sing a modified version of "Your Song" for Apu and Manjula as a Valentine's Day gift. It. Was. Adorable!

2. Britney Spears




In an episode called "The Mansion Family" Britney Spears guest-stars as the host of the Grammy Awards. While she doesn't really sing in the episode, she's seen wearing one of the outfits from her "Hit Me Baby One More Time" video.

1. Paul McCartney




Paul and his then-wife Linda McCartney appeared on The Simpsons episode "Lisa The Vegetarian" and encouraged Lisa to lead a vegetarian lifestyle. The cutest part? When Paul told Lisa that if she played "Maybe I'm Amazed" backwards, she'd hear a recipe for lentil soup!

Who's your favorite musical Simpsons guest-star? Tell us in the comments!