C3PO

C3PO was a character in the film Jedi who was worshipped by Ewoks. (PROSE: Twilight of the Gods)

Ace referred to Fortalexa's robot guard as "C3PO's big brother". (PROSE: Theatre of War)

The Tenth Doctor once introduced his "associates" Cindy Wu and Gabby Gonzalez as "Artoo and Threepio", much to their irritation. (COMIC: )

Behind the scenes
C3PO is a character in the Star Wars series and the constant companion of R2-D2. The droid's name is properly spelled as "C-3PO".