"No one making ‘Casablanca’ thought they were making a great film. It was simply another Warner Bros. release.    It was made on a tight budget ($950,000) and released with small expectations. Everyone involved in the film had been, and would be, in dozens of other films made under similar circumstances, and the greatness of  ‘Casablanca’ was largely the result of happy chance.  ‘Casablanca’ was just another studio main feature produced by Hal B. Wallis and directed by Michael Curtiz.   The fact is that even if they had wanted to, they could not have set out to make ‘Casablanca’ turn out the way it did.  It was a combination of elements and circumstances which produced a work of indefinable appeal which has endured for generations even though tastes and attitudes have changed.   You don’t set out to make a classic, you set out to make a film.

The story was from an unproduced play by Murray Burnett and Joan Alison, a play of no great consequence and written for the screen by the brothers Julius J. and Philip G. Epstein and Howard Koch (and the uncredited Casey Robinson). They struggled hard as studio hacks on assignment to get the script pages in on time, and did not plan for the fact that because the actors did not know how the film would end their ambiguous and edgy characterisations would be a major contribution to film folklore and debate ever after.

Humphrey Bogart was always best when he played the disappointed, wounded, resentful hero. In ‘Casablanca’ he is Rick Blaine, an American running a nightclub in Casablanca when Morocco was a crossroads for spies, traitors, Nazis and the French Resistance.  Into this world comes Ilsa Lund (Ingrid Bergman), the woman Rick loved years earlier in Paris. (“of all the gin joints in all the towns in all the world, she walks into mine”).  Under the shadow of the German occupation, he arranged their escape, and believes she abandoned him – left him waiting in the rain at a railway station with their tickets to freedom. Now she is with Victor Laszlo (Paul Henreid), a legendary hero of the French Resistance.

No better cast of supporting actors could have been assembled on the Warner Bros. lot – the richness of the characters, Sidney Greenstreet as Signor Ferrari, the corrupt rival club owner, Peter Lorre as Guillermo Ugarte, the wheedling little black-marketeer, Claude Rains as Captain Louis Renault, the police chief and Conrad Veidt as Major Heinrich Strasser the Nazis ‘baddie’.

Stylistically, the film is not so much brilliant as absolutely sound, rock-solid in its use of Hollywood studio craftsmanship. Michael Curtiz, the director, and the writers Julius J. Epstein, Philip G. Epstein and Howard Koch all won Oscars, as did the film itself gaining Best Picture 1943.

The final touches to the legend of Casablanca were equally incidental. Musical director Leo Forbstein oversaw the hiring of Max Steiner and the selection of two songs ‘Knock on Wood’ by M.K. Jerome and Jack Scholl and ‘As Time Goes By’ by Herman Hopfeld to be performed by entertainer Dooley Wilson, still in the first year of his film career (Dooley Wilson was a drummer who did not play piano).

The film was critically and commercially successful, and after its release its cast and crew went on to their next films oblivious to the fact that as far as popular memory was concerned, they would always be associated with a night –club in Casablanca.

The black-and-white cinematography has not aged and the dialogue is so spare and cynical it has not grown old-fashioned.

There have been two attempts to make a sequel to Casablanca, both times on television, both times a failure."  http://homepage.ntlworld.com/alm005/casablanca.htm