The web definition of a flash mob is a group of people who assemble suddenly in a public place, perform an unusual and seemingly pointless act for a brief time, then quickly disperse, often for the purposes of entertainment, satire, and artistic expression. Basically, it is when a group of people seemingly randomly start dancing synchronized. This was the Harlem Shake before the Harlem Shake.
Here we have the cast and crew from the hit CBS show The Big Bang Theory performing a flash mob. If you are a fan of the show I think that you will enjoy the character of Dr. Sheldon Cooper, played by Jim Parsons, standing in the background seemingly annoyed. The guys and girls from this show do some pretty impressive moves throughout the dance