The ironic thing about "Casablanca" being a classic and "flawless" film was that nobody really wanted to do it. It was one of three films Bogart was contracted at the time to complete within a year and everyone just wanted to get those films out of the way so they could go on to other bigger and better contracts. Like: "Oh hell, let's just get something in the can so we can get the hell outta here." It was shot in three weeks for under a million bucks. 'Fog' was in the closing scene was used to hide the poor quality of the cardboard cutout planes on the 'airfield'. If I remember my film history correctly, Ingrid Bergman was 22 when she played the role of Ilsa, and the other two Bogie films no one wanted to do were "Sahara" and "Action in the North Atlantic."
"Casablanca" goes to show what you can do when you don't try too hard. (LIke Orson Welles' radiocast of "War of the Worlds", which started out as a Halloween prank. Think he was 25 when he pulled that little number out of his hat.)
Lot of Ingrid Bergman in her daughter, Issabella Rossellini, BTW, wouldn't you say?