Fog has played a defining role in some of our favorite movies, instantly setting the stage for either romance or menace. In Casablanca, Humphrey Bogart always seems to be shrouded in fog or cigarette smoke, while Fred Astaire, in his first film without Ginger Rogers, A Damsel in Distress, woos Joan Fontaine by singing the Gershwins’ romantic “A Foggy Day (in London Town).” In the original production of Oklahoma!, Agnes de Mille used dry-ice fog in her revolutionary “dream ballet” to evoke subconscious romantic yearnings.

Source: Shroud of London | The Weekly Standard