http://blag.xkcd.com/2007/10/01/the-meetup/

xkcd readers successfully overran a park in Cambridge a week ago, and it’s taken me this long to fully recover. But boy, was it fun. Here’s a wrap-up:

Back in the spring, when I lived in Virginia, I drew this comic. The date was in the future, the coordinates were a park in Cambridge. When the date came last weekend, hundreds of people showed up.

http://xkcd.com/240/