A Swedish dance/techno song by Caramell. The songs title translates to: The Caramel Dance.
The song spread quickly on the internet for a sped up version being the music to which Popotan's Mai and Mii dance to in a fan edited video. The dance is called "ｳｯｰｳｯｰｳﾏｳﾏ(ﾟ∀ﾟ) (U-u-uma uma)" or "ウマウマダンス (Uma uma dance)" in Japan.
Interestingly, the vast majority of posts under this tag reference the visual part of the flash, which comes from the opening animation of the Popotan game and has nothing to do with the Caramell song. Later on, however, Caramell did put out a second music video of the song featuring anime/manga inspired personas doing the dance, with the exact same tempo as the original edit.