Rainbowloids
Sometime in 2007, a 2channel user started a thread where they would ask other 2ch users for a name and color, and they would draw it in a Vocaloid-like style. This resulted in the creation of 15 fanloids, who ended up becoming known as the "rainbowloids".
There were a few attempts to make the Rainbowloids into UTAU, but they mostly fell through and Teto ended up being the first VIPPERloid instead.