Protocol Droid
Anakin built C-3PO, who he often referred to as just Threepio, and the name stuck. A humanoid protocol droid designed to help make Anakin's mother's life easier, Threepio was programmed for etiquette and protocol, as well as for fluency in over six million forms of communication. His personality tends to be on the fussy and worry-prone side, but he's had a lot to put up with since he parted company with his original master.
