2-D is the very first member that Damon and Jamie came up with for Gorillaz, despite sometimes saying it was Murdoc.
Originally, auditions were held to find a singing voice for 2-D. However, Damon quickly realized that was not the way he wanted Gorillaz to work, and that the proper way to do it is to sing as 2-D himself, and instead use collaborators and guests, rather than have another singer be 2-D.