8 Star Wars Prequel Moments George Lucas Planned Way Back In 1977
6. Darth Vader's Past Was A Mystery
"The Death Star had readouts about everyone on board, except Darth Vader" - C-3PO
In 1980 everyone learnt that a lot of Darth Vader's past was incredibly subjective, but even before the series-defining decision to make him Luke's father, Lucas was keen to play up the character's mysterious past.
Although R2-D2 had the Death Star plans when the gang ended up in the space station, he'd have been silly to not have checked their records. And according to C-3PO he did; he tells us there were detailed files on everyone on board, except for Darth Vader, of whom there was no trace.
Although in the film he felt partially like Grand Moff Tarkin's lapdog, this is something that points towards his grander power; he's close to the Emperor and far from just another member of staff. It seems obvious, but given how the character had proven a major draw in the film's box office haul Lucas probably wanted to formalise it.
Even though Obi-Wan was very open about Vader's past (if missing key details), this decision to highlight his mystery shows how Vader's place in the saga was starting to shift. As these notes originate in the immediate aftermath of Star Wars' release, this could be the first official trace the story was slowly morphing into that of Darth's life.