C-3PO is a gold-plated humanoid protocol droid and a major character in the Star Wars universe. With a terrible nervous streak and a knack for getting into trouble, he provides most of the comic relief throughout the original movie trilogy. He is portrayed by Anthony Daniels in all of his movie and TV appearances.
Unknown to all but R2-D2 and a handful of others following the rise of the Galactic Empire, C-3PO (often referred to as 'Threepio") was built by the young Anakin Skywalker, who would eventually grow up to become the dreaded Darth Vader. Anakin made Threepio to assist his mother at home whilst he worked in Watto's junk shop in Mos Espa. He was still incomplete when he was first activated, having no external plating and weak joints.
Upon activation, the first faces Threepio saw were those of his maker Anakin, a Naboo girl called Padme, and the astromech known as R2-D2. He was immediately complimented by Padme, who called him 'perfect'. When he and Artoo first met, Artoo pointed out that Threepio was 'naked' since he had no plating covering his wiring and components. He would eventually recieve plating when he fell into the service of the Lars family when they bought and freed his creator's mother, Shmi Skywalker. During his time on the Lars' homestead, Threepio's job was to interpret the binary language of the farm's moisture vaporators.
Ten years after his maker's flight from Tatooine, Threepio would be reunited with his creator Anakin when he returned to seek out his mother. He would also be reacquainted with Padme Amidala and R2-D2, and accompany them when they left the planet to travel to Geonosis. Although ordered to stay with Padme's ship, Threepio left to chase after the defiant Artoo, who followed his masters into the Geonosian droid foundries. This would be the first of many misadventures between Artoo and Threepio over the years. During their venture into the factory, Artoo pushed Threepio off of a platform and sent him falling into the B1 droid production line, where his head was severed from his body and ended up being welded to a battle droid body. A B1 head was attached to his own. When the Seperatist Droid Army advanced on the Jedi in the Geonosian arena, Threepio marched into battle with them, his mind partially corrupted by battle droid programming. His head would be severed again in the battle and would be reattached to his own body by Artoo, with Threepio himself having only a vague recollection of the events.
After the Battle of Geonosis, the Clone Wars spread out across the galaxy. During this time, C-3PO became a full-time servant for his maker Anakin's new wife, Padme, aiding her with diplomatic issues which would require interpretation. In order to appear more presentable, Threepio had his grimey tin plating replaced with glimmering gold plating, which he has kept ever since. His service to the Senator would last till the end of the war, at which point Anakin had turned to the dark side of the Force and Padme had died during childbirth. Threepio and Artoo were passed on into the service of Captain Antilles, commander of the Tantive IV. Initially, Threepio was excited to tell the newborn Leia Organa all about her true family. However, his memory was erased before he had the chance, thus he had no recollection of his maker Anakin, Padme, or anything since his activation.
In the year 0 BBY, the Tantive IV was attacked by an Imperial Star Destroyer commanded by Darth Vader. R2-D2 had been entrusted by Princess Leia Organa with the schematics for the Empire's new battle station - the Death Star - and he and C-3PO were jettisoned to the desert world of Tatooine. After landing, the two droids argued over which direction to take to find a settlement. Artoo insisted on following his secret mission, and Threepio stubbornly walked off in the opposite direction. The two would be reunited aboard a Jawa Sandcrawler after both droids were captured by Jawa scavengers. They were later sold to the Lars family and their nephew Luke Skywalker, the son of Threepio's forgotten creator Anakin. Whilst being cleaned up, Artoo showed Luke a partial message from Princess Leia for Obi-Wan Kenobi, who was living in exile beyond Tatooine's Dune Sea. Artoo tricked Luke into removing the droid's restraining bolt, which allowed him to run off into the desert during the night. Threepio accompanied Luke out into the Jundland Wastes to find Artoo, but when they found the astromech they were ambushed by Tusken raiders. Threepio was torn to pieces but would later be repaired when Obi-Wan Kenobi came to the rescue and took Luke and his droids back to his home.
After Luke discovered the truth about his father and joined Obi-Wan on his journey to Alderaan, Threepio and Artoo accompanied him. Both Threepio and Artoo would end up in a number of difficult situations during their travels, but they would survive and eventually be taken under the protection of the Rebel Alliance.
After the Battle of Hoth, Threepio was separated from his master and his counterpart Artoo. He found himself aboard the Millenium Falcon with Han Solo, Chewbacca and Princess Leia as they were pursued by Darth Vader's fleet. As hard as Threepio tried to be of service to Captain Solo during this time, his efforts awarded him not so much as a single compliment from the aggravated smuggler. When the Falcon tried to take shelter from the Empire at Bespin, Threepio wandered into a room in Cloud City where he was confronted by stormtroopers, who shot him on sight. Chewbacca would later find Threepio's parts in a junkyard and would haphazardly put him back together after the group had been arrested by Vader's troops. He would be fixed completely later back aboard the Falcon and reunited with his master and Artoo.
Threepio's next adventure would take him back to Tatooine as the Rebels tried to rescue the carbon-frozen Han Solo from Jabba the Hutt. Threepio and Artoo were taken into Jabba's palace and were offered to Jabba as gifts in exchange for Solo. Of course, Jabba made no bargains and kept the droids anyway, and Threepio was assigned to be Jabba's interpreter during audiences with bounty hunters and important figures. When Luke Skywalker and Lando Calrissian executed their rescue plan over the Pit of Carkoon, Threepio was attacked by Jabba's pet and had one of his optics pecked out.
Later, when the Rebels landed on Endor for their strike against the Death Star II's shield bunker, Threepio and friends were captured by the native Ewoks. When they saw Threepio, however, they began to worship him as a god. Using Threepio's communication skills and a little of Luke's Force power, Threepio convinced the Ewoks to release the Rebels and to help them in their fight against the Empire.
C-3PO always carries out his duties in a sophisticated manner, but can be uppity at times and becomes terribly nervous in tense situations. As well as being a pessimist, he has a tendency to blame R2-D2 for all the bad things that happen to him (which half the time are indeed Artoo's fault anyway).
C-3PO has a humanoid frame but does not move with the same grace and dexterity as a living humanoid would. He walks in small, shuffled steps with his arms always hanging out in front of him. When first built, his movements were flimsy and he had nothing to cover his circuitry. He would be fitted with coverings by the time he began working for Cliegg Lars and would later be fitted with gold plating during his service to Senator Amidala. His primary function is interpretation and assisting with relations between humans, droids and aliens. He is programmed with an extensive vocabulary and is perfectly fluent in over 6 million forms of communication.