If you're not sure what a flashmob is then now is the time to learn. It's a cultural trend spreading via the internet. Check out this video of a flashmob done in Grand Central... http://www.youtube.com/watch?v=jwMj3PJDxuo A flash mob is a large group of people who assemble suddenly in a public place, perform an unusual action for a brief time, then quickly disperse. Flashmobs are a fun way to take your humor, social, and theatrical skills and put them to the test, and a great way to ma …