As the long-running cartoon celebrates its 500th episode, we look back at some of the show's most memorable celebrity guest stars.

Everyone's favourite long-running, all-American cartoon series celebrates its 500th episode this weekend, and has featured some unforgettable celebrity cameos during its long run.

Rock and pop royalty such as The Who (pictured above in their 'Simpsonized' form) Paul McCartney, Britney Spears, Aerosmith and Sting; Hollywood stars as diverse as Jack Lemmon, Mickey Rooney, Daniel Radcliffe and Reece Witherspoon, comedic talent like Ricky Gervais, Paul Rudd, Ellen deGeneres and Jonah Hill and sports icons including the Williams sisters, Ronaldo and Joe Frazier have joined luminaries from the fields of art, literature, science, politics, business and even space exploration in lending their voices to the animated antics of the inhabitants of Springfield.

And those are just the ones we've not included on our list! The Simpsons holds the Guinness World Record for the most guest stars ever on a TV show, but we've been able to narrow them down to bring you a few of our favourites. Click on to find out who we've picked.

See also: 'The Simpsons' - the faces behind the voices!

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