Nyanyanyanyanyanyanya! is a series of highly repetitive videos built around an anime character swaying side-to-side or bobbing up-and-down with "Nya's" and other objects popping up in the background. Since the debut of the original version featuring Hatsune Miku synthesizer by Nico Nico Douga user "daniwellP", the addictive song has spawned dozens of remixes and MAD videos starring a wide range of anime-related characters.
Nyan Cat Theme
The song gained much of its international popularity in April 2011, when YouTuber saraj00n posted a remix video titled Nyan Cat, using comic illustrator PRguitarman's GIF animation of a flying kitten with the body of a strawberry pop tart.
The first Nyanyanyanyanyanyanya! video  was originally produced by the Japanese musician daniwellP and uploaded via Nico Nico Douga on July 25th, 2010. Although it may sound like Miku isn't singing, but she is actually singing "nya- nya-" from the beginning to the end, according to the site's encyclopedic entry. As of April 2011, this video has more than 800,000 views on the Japanese video-sharing hubsite.
The word "Nya" is a Japanese informal word denoting the cry of a cat, like "Meow" in English, with a specific connotation of "cuteness". It is very popular amongst NND users. It is also the name of Nico Nico Douga power user "Nya", who pioneered the genre of 3D-model based MikuMikuDance (MMD) videos in November 2007. It also refers to the filename extensions for NND's Live Effect animation files (.nya).
On October 18th, 2010, NND user uniql  posted a remix version titled "NEKOMATAGI REMIX" featuring a female anime character:
On October 19th, 2010, NND user daniwellP responded to the remix video:
It is also interesting to note Nico Nico Douga's inaugural Miku Miku Dance (MMD) Cup in July 2008 was entirely based on remixes of daniwellP's "Nyanyanyanyanyanyanya" video, serving as the gateway event in emergence of user-generated derivatives.
There are several live-karaoke instances of the song, a popular Japanese fad known as Utatte Mita (歌ってみた), or "I've tried singing it," as well as instrumental covers known as Hiite Mita (弾いてみた), or “I tried playing it.”
On April 5th, 2011, YouTuber saraj00n posted a video titled Nyan Cat, using comic artist prguitarman's Pop Tart Cat animation set to the well-known Japanese Vocaloid song Nyanyanyanyanyanyanya by Japanese artist daniwellP looping in the background. The video gained over one million views in its first two weeks, spawning a variety of tributes and derivative media. For more information, please read our entry on Nyan Cat.
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 Nico Nico Douga – RE: 【初音ミク】Nyanyanyanyanyanyanya!(NEKOMATAGI REMIX) / Posted on 10-19-10