Flash mobs are all the rage these days. You never know when you'll be walking through the mall, grocery store, or any public setting and witness one of these.

The cast and crew of 'The Big Bang Theory' gave the guests in their studio audience, and some of the production crew, a surprise when the broke into a flash mob on the set.

Of course it would be the massive Carly Rae Jepsen hit 'Call me Maybe' that they did it too. Kaley Cuoco, who plays Penny, posted on her official Facebook page that she was super excited to be part of her first flash mob.