The Harlem Shake internet meme took off in early February 2012. The meme featured videos lasting about 30 seconds and feature part of the 2012 song "Harlem Shake" by electronic musician Baauer. The videos all start with one person dancing, while those around them go about their business. The video then cuts and suddenly the screen is filled with people in crazy costumes dancing. The videos end with a drop to slow motion.
The Supernatural version, which was dubbed the Supernatural Shake, was the brainchild of Jensen Ackles. Source #1. According to director Guy Bee "He showed me samples of others and we agreed that day we had all the elements to do it!" Source #2.
The video was shot on 25/2, but wasn't posted online until 6th March due to the necessity to get clearance from Warner brothers, who produce Supernatural. The video garnered two million views in the first 48 hours.