C-3PO (or See-Threepio, spelled phonetically) is a protocol droid fluent in over six million forms of communication -- although some of them appear quite rusty. Both C-3PO and his astromech counterpart, R2-D2, have remained in the Skywalker family for several generations.
C-3PO in the Prequels
Anakin Skywalker built C-3PO out of spare parts on Tatooine around 32 BBY. Some of his original parts date back to nearly a century earlier, when they were forged by Cybot Galactica on the planet Affa. He was never able to afford plating to cover the droid's exposed wiring. When Anakin left Tatooine to join the Jedi Order, C-3PO remained with his mother, Shmi Skywalker. She later covered him in dull, silver-colored plating.
When Shmi married Cliegg Lars, she took C-3PO with her. Anakin was reunited with C-3PO when he returned to Tatooine to find his mother. Cliegg's son Owen gave C-3PO back to Anakin; he in turn gave C-3PO to Padmé Amidala as a wedding gift. His silver plating was replaced with gold during the Clone Wars.
After Anakin fell to the dark side and Padmé died, R2-D2 and C-3PO fell into the possession of Obi-Wan Kenobi. He gave the droids to Bail Organa, the Senator from Alderaan who adopted Anakin's daughter Leia. Organa had C-3PO's memory wiped to hide the truth of Leia's parentage, but kept R2-D2's memory intact.
The droids were assigned to the Tantive IV, but were forced to escape during a pirate attack. For several years, they were acquired and then sold or abandoned by nearly two dozen different owners. During their travels together, R2-D2 and C-3PO developed a familiar camaraderie.
C-3PO in the Original Trilogy and Beyond
R2-D2 and C-3PO eventually found their way back to Princess Leia, now a member of the Rebel Alliance. When her ship was attacked on the way to contact Obi-Wan Kenobi on Tatooine, Leia hid secret plans inside R2-D2. At R2's insistence, the two droids escaped to the planet's surface, where they were captured by Jawas and sold to Owen Lars -- who did not recognize C-3PO -- and his nephew, Anakin's son Luke.
Despite C-3PO's fussing, R2-D2 found his way to Obi-Wan Kenobi to deliver the message. The droids accompanied Obi-Wan, Luke, Han Solo and Chewbacca as they rescued Princess Leia from the Death Star, then remained with the Rebel Alliance for the rest of the war. The droids were frequently separated, however, with R2-D2 operating as the mechanic aboard Luke's X-wing and C-3PO serving aboard the Millennium Falcon.
C-3PO briefly served as a translator for the gangster Jabba the Hutt; Luke had give the droids to Jabba as part of a ruse to rescue Han Solo. Later, C-3PO was forced to impersonate a god in order to communicate with the Ewoks, a tribe of small furry aliens on the forest moon of Endor. C-3PO's story of the Rebels' struggle against the evil Empire helped convince the Ewoks to join the fight.
After the end of the Galactic Civil War, C-3PO primarily served the Solo family, taking care of Han and Leia's children and grandchild.
C-3PO Behind the Scenes
R2-D2 and C-3PO were inspired by Tahei and Matashichi, peasants and comic relief characters who travel with a princess and a general in Akira Kurosawa's film The Hidden Fortress (1958). C-3PO's appearance was inspired by the robot in the dystopian sci-fi film Metropolis (1927). Since his face is expressionless, most of the droid's fussy personality comes through in his voice.
In most Star Wars media, C-3PO is portrayed by Anthony Daniels, who used his training as a mime artist to project emotion in C-3PO's movements. Daniels is one of only two actors to appear as their character in all six Star Wars films -- the other is Kenny Baker as R2-D2 -- and the only actor to play the same character in all six films, the Original Trilogy radio dramas, three cartoon series and the Star Wars Holiday Special. Tom Kane, Ross King, and Jim Ward have also voiced C-3PO in various video games and radio dramas.