SEOUL, South Korea — Ordinarily, a star turn on “The Ellen DeGeneres Show” teaching Britney Spears his dance might be one of the surest signs that a performer has made it. But this week, Park Jae-sang, the South Korean phenomenon behind a dance video called Gangnam Style, got an even clearer sign of success. North Korea — so cut off from the world that satellite shots show most of the country plunged in darkness at night — parodied the video.

The North used the video to score a propaganda point, making fun of a South Korean presidential candidate. But one thing was still clear: While ordinary North Koreans are unlikely to have seen the video (access to the Internet is severely limited), Gangnam Style is a big enough hit that even reclusive apparatchiks know of it.

Why the original video, released in July, has gained such popularity is anyone’s guess. In it, Mr. Park, 34, does a “horse riding” dance that looks vaguely like what children do when they hop around pretending to be galloping. He raps and dances around Seoul, all in the company of pretty women and to a song with an infectious beat.