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After visiting the set of Close Encounters of the Third Kind (1977), George Lucas was sure Close Encounters would outperform the yet-to-be-released Star Wars at the box office. Steven Spielberg disagreed, and felt Lucas' Star Wars would be the bigger hit. In the idea of getting a compensation if Star Wars were a box office bomb, Lucas proposed a gentlemen's pact (as they were close friends from the university), trading two and a half percent of the profit on each other's movies. Spielberg accepted the deal, and he still receives two and a half percent of the profits from this movie (as Lucas receives the same from the Close Encounters).
George Lucas was so sure this movie would flop that instead of attending the premiere, he went on vacation to Hawaii with his good friend Steven Spielberg. It was on that vacation that they came up with the idea for Raiders of the Lost Ark (1981).
In early drafts of the script, R2-D2 could speak standard English, and he had a rather foul vocabulary. Although all of R2's English speech was removed, many of C-3PO's reactions to it were left in.
George Lucas' decision to accept a lower salary on the movie in exchange for full merchandising rights was considered a fool's gamble on his part. Although some movie-toy combinations had done moderate retail returns at the time, they had never been major money-earners because of the long gap between when a movie would go through its theatrical run and when any products based on it would be available. This movie, however, was such a phenomenon that it reached the holiday 1977 sales period in full swing, and changed the way how movies were merchandised forever.
James Earl Jones and David Prowse, who play the voice and body of Darth Vader respectively, never met.
Harrison Ford didn't learn his lines for the intercom conversation in the cell block so that it would sound spontaneous.
Robert Clarke: The white-mustached Admiral in the Death Star conference room was later given the name Wullf Yularen, and developed as a character in other media, such as Star Wars: The Clone Wars (2008).