Not the Marx Brothers movie, but a Howard Hawks comedy starring Cary Grant, Ginger Rogers, and Marilyn Monroe (in one of her first roles, I think). My wife and I watched it last night, and while not a "laugh until your sides ache" film, it was still quite a bit of fun. UPDATE: not one of Monroe's first roles. It wasn't a very demanding part, but she did it well.
One aspect that was especially gratifying is that the plot revolves around a scientist's efforts to create a "youth serum" that will restore people to a younger state of health. Because this was made in 1952, there are some hints that it produces some libidinous effects on the married couple (played by Grant and Rogers) who end up with it, but done with enough subtlety that I suspect that many children and some teenagers watched the film when it came out and completely missed this part. Of course, to be subtle with such subject matter requires a skilled screenwriter. You can see why this is not done today.
We also enjoyed Sabrina (1954) the other evening, with Audrey Hepburn, William Holden, and Humphrey Bogart. This is something of a Cinderella story, with some very entertaining twists to it.