Don, and others... filter these on Mudcat. The very first flash mobs (recall... don't trust MY memory because *I* sure as heck don't) were in La Belle Province, Canuckistan. There are threads. And those flash mobs are excellent! And they were posted in threads here at mudcat many moons ago.

Searching at YT is okay but it doesn't bring up the really good ones... well, the ones I thought were GOOD.