I wonder if anyone has already noticed/commented upon this. Have you ever wondered what would have happened if C3-PO were to meet Darth Vader in any of the Classic Trilogy films? Darth Vader would have surely recognized his creation, right?
Well, there was one instance where it was possible for them to meet; on cloud City, when Lando betrays them to Darth Vader. The entire group enter a room where Vader is waiting for them. But C3-PO is not with them here! Why? Because just before that he was blasted into pieces by the Ugnaughts!
And in the scene right after, Chewy is putting him back together again! So why did C3-PO have to be in pieces for only 10 minutes in the film?
So that Lucas did not have to put him in the awkward position of facing Vader! It seems so obvious now that we know…