Dang, they sure know how to have fun on the set of The Big Bang Theory. While taping tonight’s episode (The 43 Peculiarity”), Kaley Cuoco had the bright idea to surprise the audience and the writers with a flash mob that involved the cast and crew.

Kaley’s sister Bri choreographed the moves during the Oct. 23 taping and Jim Parsons, as the glorious Sheldon, got to enjoy the last word. Check out EPs Chuck Lorre, Bill Prady, and Steven Molaro in the directors chairs. Clearly, the boys don’t know quite what’s going on: