Brian Phillips writing for Grantland:
The real story of Star Wars is the redemption of Darth Vader, while Captain Renault’s redemption in Casablanca is just a by-the-way bonus. But the resemblances are intriguing. Why do they exist? I don’t think the answer is that George Lucas deliberately copied Casablanca; I think it’s that Star Wars and Casablanca are both made out of a million spare parts from other and older stories, and some of the action-romance archetypes that George Lucas drew upon in Star Wars had also been drawn upon 35 years earlier by the committee of accidental geniuses that made Casablanca.
I normally wouldn’t have seen a connection between these two films in a million years, but Brian’s piece makes a compelling, albeit indirect, arguement.