Hatsune Miku
Since the success of her Vocaloid 2 package led to an expansion of marketing possibilities, most of the mass marketing has come after her initial release as a response to her popularity and has been on going since 2008. Even with the addition of other Character Vocals, Miku's name continues to be used as the primary source of marketing for Crypton Future Media, to the point where most products for their Vocaloid related products will usually only feature Hatsune Miku's name. In March 2012, the Nomura Research Institute estimated that the sales of all Hatsune Miku brand goods added up into the region of since her release in 2007. Her name is easily the most recognizable of all Vocaloids.
SF-A2 Miki
Her design was unique among the VOCALOIDs. She had no references to YAMAHA based musical instruments like other VOCALOIDs and was designed to look cybernetic, giving her a more sci-fi look than most other Vocaloids at the time. According to information that came from the 2012 redesign, miki was designed to look like she was made out of an inorganic material and was conceptualized as an android. Her body is designed to look like that of a child, but also give her the overall appearance of a young teenage female. Though she is an android, she is covered in muscles made from various materials such as carbon nanotubes, but were made loose to give a mild deformed look about them. Having an immature-looking body allowed her to appear younger than she looks, similar to how Hatsune Miku and Kagamine Rin could do the same.