http://www.youtube.com/watch?v=CF0A0I6cqmI

Hatsune Miku IS NOT an anime character (there’s no official manga or anime… yet), she’s actually a character developed to represent a specific voice on a voice synthesizer app called Vocaloid, which also has tons of other characters and voices.

For those who don’t know, voice synthesizer apps are computer softwares used to create voices for determined purposes… be it to replace singers in music, or to dictate text.
Vocaloid is famous because, at least for japanese lyrics, it has reached the closest resemblance to human natural speech ever, something extremely hard to achieve.
And it’s an incredibly positive thing because it allows music composers to create music without the need to find a talented singer (a controversial issue, I know).
Here’s a very thorough video explaining the phenomena… use the YouTube menu to turn the closed caption english subtitles on:

http://www.youtube.com/watch?v=xBZOlipfjkQ

Back to Hatsune Miku, people liked her design so much she eventually spawned a huge ammount of products (like posters, games and figures) and fan made music videos, animations, doujinshi, etc… reaching a fame status few other anime characters have.
Probably due to her not having an “official” personality, so people can spin it the way they want.
I hope this helps those who were in doubt, and that it also spreads the trend.. I realize there are tons of talented composers out there that ends not having their value recognized because of flawed musicians performing their stuff, so it’s really amazing to see composers like ryo getting attention and being able to show the world their work.