is what wikipedia says about flash mob.
This 'unusual action' can vary from sudden pillow fights, freezing, falling asleep or whatever crazy thing you can think of.
I don't know if you've ever heard of it, but I think you should. It's fun to do and fun to watch!
I found this fantastic japanese flash mob yesterday ;) :
Not so long ago, someone started a flash mob troup in the Netherlands called 'Shoqs'. I took part in their first flash mob, which was inspired on a flash mob called 'frozen grand central' of the new york flash mob group called 'improv everywhere'. With a group of about 300 people we stood frozen for 5 minutes at the central station in Utrecht. It was so much fun, because while I was standing there (and having a hard time trying to not blink my eyes to much), I heard people saying things like 'what's going on?' and 'this is so cool'. Well, you just have to look at these 2 videos. The first one is the one in New York and the second is the one in Utrecht (I'm not in this video, but if you watch some other videos you can see me standing in my purple skinny)
You should all join me in the next shoqs flash mob!