Hatsune Mix (also known as Hatsune Miku: Unofficial Hatsune Mix) is a manga created by Kei, the original artist of the Vocaloid named Hatsune Miku. A comedy/parody manga, it features Miku and her fellow Vocaloids in different situations. Each chapter is a self-contained story, so there is little continuity.
Mermaid Mix (Volume 1, Chapter 9)
In a parody of The Little Mermaid, Miku manages to convey her love towards the prince. This undoes the witch's magic, restoring her voice and turning her back into a mermaid. But it also doubles Miku's weight (the witch said there would be a bonus).