Apparently "flash mob" dances are still a 'thing', because the cast and crew of "The Big Bang Theory" recently did one to Carly Rae Jepsen's "Call Me Maybe".

It was all organized by Kaley Cuoco, who plays Penny.  She got her sister to choreograph it, and about 40 or 50 people surprised the producers by busting it out during a live taping a few weeks ago.

CBS posted the video on YouTube yesterday.  (--Search for "The Big Bang Theory Flash Mob."  The music starts at :13, and the cast joins in at :33.)