Was Captain Renault smitten by that young bride?
I was watching Casablanca recently and I think that Captain Renault might have had a bit of a crush on the young bride that comes to Rick for help. If you read between the lines you can see him look jealous when the bride gives Rick a hug when leaving - a hug that Captain Renault is obviously too shy to try to win! His jealousy builds throughout the scene and, after everyone sings their old college song, he shuts the nightclub down for no reason but sheer spite!
He also asks Rick why he (Rick) would spoil "A Little Romance" for him (Renault). At first I thought that he (Rick) had given away the ending to the film (A Little Romance) to him (Rebault), but upon investigation that film (A Little Romance) was not released in Africa until 1979.
Therefore we can assume that Renault was talking about his unrequited feelings toward the young bride. You can see the wistful look in his eyes when she and her husband meet him and she calls him by the honorific "Captain Renault" instead of Louie as he would have preferred.
We can only hope that he overcomes his crippling shyness in the free French garrison!
"Professor Marvel never guesses - he knows!"