Nyan or nya is the Japanese for meow (the cat cry). The song is an endless loop of Miku saying "Nya" over and over while pouncing. On April 5, Saraj00n uploaded video of a Poptart Cat with UTAU Momone Momo's voice on YouTube. The song became popular, under the name of Nyan Cat.
Non-VOCALOID fans (fans of the Nyan Cat video) and VOCALOID fans debated on the originality, some incorrectly claiming Nyan Cat came first, while the latter correctly claimed the song was by daniwellP. The confusion died down after a few months prior to the Nyan Cat Video, but it left a bad impression on both sides.