Before Gangnam Style, Park Jae-sang, known as Psy, was no rookie. He was a veteran South Korean artist working on his sixth studio album, with national hits like Champion and a home audience that expected a fresh, memorable dance every time. To deliver one, he and his choreographer went without sleep for 30 nights, testing panda moves and kangaroo bounces before landing on the invisible horse trot. The goal was simply to make local fans laugh.

This episode explains the joke and how it escaped. Gangnam is a wealthy Seoul district that Psy likened to Beverly Hills, and his target was the posers who go into debt to look refined. His rule was dress classy and dance cheesy. The video was shot in 48 hours, mostly outside Gangnam, and released in mid-July 2012. Then celebrity tweets carried it abroad, and a satirist found himself treated as a diplomat, a stock market force, and the face of the Korean wave.

• The video drew about half a million views on its first day, then spread after T-Pain, Robbie Williams, Katy Perry, and Tom Cruise shared it, peaking at over 9 million views a day.
• Psy flew to Los Angeles, met Scooter Braun, and signed with Schoolboy Records by early September.
• It became the first internet video to reach one billion views, overtaking Justin Bieber’s Baby.
• UN Secretary-General Ban Ki-moon hailed the dance as a force for world peace and performed the horse trot for cameras.
• Shares in DI Corporation, the semiconductor equipment company owned by Psy’s father, rose more than 500 percent as retail investors piled in.