2000, Elizabeth B. Davis, Myth and Identity in the Epic of Imperial Spain, University of Missouri Press, →ISBN, page 216,
Perhaps it is no accident that one of the most poignant moments in the whole Star Wars trilogy is the scene in Return of the Jedi where the protocol droid C-3PO relates the story of the Galactic Civil War for the assembled Ewoks in a language only they can understand.
2002, Pamela Rice Hahn and Jesse Flores, Journey to the Center of the Internet, Syngress, →ISBN, page 59,
“But moving right along, let’s talk about protocols,” Dr. F. continued.
Finally, a movie reference I understood! Finally, something I could get excited about! “Like C-3PO!” I shouted. “He was a protocol droid!”
2004, William Sims Bainbridge (ed.), National Science Foundation, Berkshire Encyclopedia Of Human–Computer Interaction: When Science Fiction Becomes Science Fact, Berkshire Publishing Group LLC, →ISBN, page 469,
C-3PO is a protocol droid, or translator, whose function is to help humans communicate with aliens and machines.