You'll never know who these people really are in this movie. They have no background. They just appear in the Empire State Building in order to get the story rolling. And roll it does. It's a very superficial, pretty inconsequential, and funny comedy. Who cares who the characters are or were, anyway? The thing most important is physical and sexual and all the jockeying that goes on before the relationship reaches that point. It turns out to be a comedy-writer's paradise. Of course in the end they will get married to at least throw a bone to social mores. Holden is near top form and Niven, as his older upstairs neighbor whose daughter was Holden's girlfriend, is classic.
Review of The Moon Is Blue
