The Aluminum Falcon said:

Casablanca 2: SAVING ILSA

Very shortly after the ending of Casablanca, the plane to Lisbon crashes, killing Victor; however, Ilsa survives but is lost in enemy territory. Rick and a rag-tag group of friends, including Sam, Renault, Ferrari, and an actually-alive Ugarte, take some weapons and go rescue her. Rick gets the girl at the end.

This movie would be made using 3D CGI models based off of photographs of all the actors.

I've read somewhere a sequel actually was proposed, but obviously never made.

There was a Casablanca tv series in the 80's, set before the events of the movie. So that counts as a prequel?

And let's not forget "Overdrawn at the Memory Bank". ;)