Trivia: There was a false page in the original script in order to fool all of the people working on the film. This was to keep it secret that Darth Vader was Luke's father. Only George Lucas, the producers and James Earl Jones knew the truth. Mark Hamill was told just moments before filming this scene so his reaction would be right, while David Prowse read the lines from the original script "Obi-Wan killed your father."
oldbaldyone
29th Sep 2004
Suggested correction: Mark Hamill stated multiple times that he knew for over a year about the twist. It was a secret for the remaining cast though.
oldbaldyone