For posters here, I'm using this as a reference point for members of the Zombie Flash Mob facebook event...Please ignore this unless you plan on attending.
So basically, here's how it will work.
At 11:55 or so (basically anytime before 12:00, depending on how long you feel like pretending you're dead), everyone is gonna either lay down or sit down (if you're not cool enough to lay down) until the belltower chimes at 12:00. When the bell chimes, everybody will rise.
Remember you're pretending to be a zombie. So...act like one. Walk slow, moan a lot...I think the only word anybody should be allowed to say is "brainssss"...pretend your limbs are heavy and sort of shuffle/drag yourself. If you feel like rocking some fake blood, then do it. I may bring some and chill around the pit for anybody who feels like going the extra mile.
I think attacking random people might be cool, but it could also get people annoyed/pissed. So choose your victims wisely? Maybe shuffle to the Student Union and moan and slam on the glass or something. There is room for creativity, just don't actually bite anybody.
This won't last for more than 5 minutes. I'll have a whistle or something so everybody knows when to disperse.
Here's a video of one in San Fran, but I think we can do better.
Post with suggestions and such if you have any. If not, I'll see ya there.