"Play it again Sam." It's the line famously quoted from a scene in "Casablanca," although what actor Humphrey Bogart actually said was. "Play it, Sam." Not that the film's writers will mind the misquote, given their screenplay for "Casablanca" is now so universally admired it has been voted the greatest screenplay of all time by the Writers Guild of America. The Bogart classic topped the list of 101 greatest screenplays, closely followed by "The Godfather" (its sequel also made it into the top 10). Christine Sams reports in the Sydney Morning Herald.