The documentary below was made in 1977 at the same time as the blockbuster hit was being filmed and takes us behind the scenes, with C-3PO and R2-D2 as our tour guides. It shows how the various special effects were produced at a time when CGI was not available. Interestingly, they do not reveal the actors behind Chewbacca, C-3PO and R2-D2. The last was played by Kenny Baker who died last week at the age of 81.
What I also found interesting were the comments by George Lucas. I had always been under the impression that Lucas had the storylines for the entire series mapped out before he made the first film but his remarks in the documentary suggests that this was not the case, though I do not understand then how the first film became called Part IV. The clip also shows a scene in which Obi Wan Kenobi tells Luke that Darth Vader killed his father, which seems to contradict what was revealed in later films. Maybe those who are much more steeped in the Star Wars folklore can clarify.