David Letterman has seen thousands of musical acts play The Late Show stage before, but none have ever been quite like Hatsune Miku. Miku is Japanese and sports calf-length blue ponytails, but what truly sets her apart is that she doesn’t really exist.

Hatsune Miku (Japanese for “the first sound from the future”) is a Vocaloid, a Japanese singing voice synthesizer. Miku’s voice and blue-haired avatar have made the creation an inescapable entity in Japan, with the character dominating all aspects of Pop culture, including music, video games, advertising, merchandise, and “live” performances.

The biggest key to success for Miku and her fellow Vocaloid characters is their boundless potential for customization. Since Miku’s musical heart is a software sample database, all her songs are composed by the program’s users. High profile producers have created hits using the Vocaloid software, but millions of everyday fans have also made Miku and her friends the conduit of their own creativity. In addition to music, fans also create videos, art, and of course, cosplay, to celebrate all things Vocaloid.

With an English-language soundbank available and the Vocaloid sensation already thoroughly embraced by the Otaku community, Miku’s creators are now hoping to take the phenomenon worldwide.

Via a live band and a 3D screen projection of the character, Miku recently opened concerts for Lady Gaga. Now, hoping to gain an even greater U.S. presence, Miku’s creators are holding an art expo and concerts in New York City this month.

Miku’s arrival in NYC sparked interest from Late Show producers, and on Oct. 8, history was made when Miku made her U.S. television debut.

Fan reaction was mixed, with some complaining that the choice of song was not the best, especially delivered in somewhat choppy English. Others were just delighted to see their virtual idol on American TV at all. As for Dave, the 67-year-old host seemed a little freaked-out by Miku, declaring after her performance, “It’s like being on Willie Nelson’s bus.”

Watch Hatsune Miku’s Late Show appearance below and let us know what you think of this unique cyber-star!

http://youtu.be/qA5pIpdQEr0