It's the dance craze that's sweeping the net:
So what is this?
まっさらブルージーンズ (Romaji: Massara Blue Jeans; English: Brand New Blue Jeans) is an Indie-Single of the Hello! Project group °C-ute. The single was released on 2006-05-06 at the second to last date of the Morning Musume Concert Tour 2006 Haru ~Rainbow Seven~, where °C-ute opened the show. It is also on sale at Fanclub Events and at the Hello! Project store.
But what's cool is that other people are doing their own versions of the video: