The Simpsons, the long-running US television animated comedy show, reached its landmark 500th episode Sunday, with an appearance from controversial WikiLeaks founder Julian Assange. America\'s most famous dysfunctional cartoon family have played out their lives before a worldwide audience for over two decades since the distinctive yellow characters Homer, Maggie and children Bart, Lisa and baby Maggie first burst onto American TV in 1989. The series has become the longest-running comedy in US television history and in its 23rd season is currently the longest-running primetime scripted show. In the 500th show, Homer and Marge discover Springfield residents are holding a secret meeting to kick them out of town, for all the trouble they\'ve caused over the years. After being sent into exile, the Simpsons arrange to meet with Assange in a bid to clear their names. The show\'s executive producer Al Jean acknowledged last month that Assange, who leaked massive amounts of sensitive diplomatic and military documents, was a controversial figure. \"There was discussion internally whether or not to have him on the show, but ultimately we went ahead and did it,\" said Jean in Entertainment Weekly. He added \"there\'s nothing we did that has anything to do with the legal situation that he\'s in.\" Assange is wanted in Sweden for questioning about allegations of rape and sexual assault, and he fears extradition to the United States for possible prosecution for the leak. \"We wanted to make sure it was satirical, and he was willing to do that,\" Jean added. \"Thanks for 500 shows,\" the show said in a note attached to the end of Sunday\'s episode. \"All we ask is that you go out and get some fresh air before logging on the Internet and saying how much this sucked.\" The Simpsons has a history of including high profile guest appearances, from Hollywood stars and musicians to politicians -- including former British prime minister Tony Blair -- and famously elusive figures such as US novelist Thomas Pynchon and British graffiti artist Banksy. Over the past 20 years, it has entered into the national and global consciousness as an icon of television entertainment. It\'s success has surprised even creator Matt Groening, the creative spark behind the family that lives in the shadow of a nuclear reactor, in a fictional town called Springfield. \"Audiences were ready again for a prime-time animated TV show,\" he told the Los Angeles Times on Saturday on the eve of the 500th episode. \"We were the first out of the gate and, using a very conservative template of a family sitcom, found a way to tell jokes in many different styles,\" he said. \"It\'s really crazy that something so quirky is so popular, but whatever that mix is, it works.\"