Wednesday at 5:30pm until Sunday, February 12, 2012 at 8:00am
more info
Also, if some fans can stomach watching the seasons after the 9th or ten they can win a lot of D'oh! Sadly all spaces for the event have been filled so you can watch people watching television for money.
"Beginning on Wednesday, February 8th, 2012, fans will come together to watch up to 500 continuous episodes of The Simpsons in an attempt to break the current Guinness World Record of 86 hours, 6 minutes and 41 seconds for the longest continuous television viewing. The contest winner will take home a $10,500 prize and an array of The Simpsons merchandise, including products exclusively designed to commemorate the 500th episode"
There's also a vague part about interactive elements at the showing with animation cells, so maybe some fun pictures can be taken. I'm not sure, because all it says is interactive elements meaning someone in pr couldn't care less about the event and had an intern write up what was happening.
Yet, probably some cool simpson stuff. I can only guess that something cool will happen there when the 500th episode airs, maybe Matt Groening will katamari a ball of money down from his mansion made of money.