Miku Hatsune is a 'character' from the Vocaloid Character Vocal Series synthesiser developed by Yamaha Corporation
Overview
On August 31, 2007, Miku Hatsune was the first released installment of the Vocaloid2 Character Vocal series. The data for the program was created by looking at samples of Saki Fujita. This speech synthesizer was initially made to create J-pop songs, but it eventually broadened into other genres of music.
The name of her character is comprised with the characters for Hatsu (First, 初); Ne (Sound, 音); and Miku (Future, 未来).
Her popularity increased because of Nico Nico Douga, a Japanese video site. In this site, users started making original compositions as well as remakes of released songs and people started collaborating on different projects. Due to her of her growth in popularity, she spawned different figures in the market and even has her manga series and video games out.
Appearances in a Series
She is parodied in (Zoku) Sayonara Zetsubou Sensei. In the episode she appears in, she (along with other people/characters) tries out to be the voice of Meru Otonashi, a mute girl who only talks through text messaging on her cellphone. She also appears in Lucky Star OVA where Kagami Hiiragi is cosplaying as Miku.
Manga Series
There is a manga about her titled Hatsune Mix, illustrated and written by KEI, where the different Vocaloid2 mascots make an appearance. However, its main focus is Hatsune Miku.