Duck Soup (1933)

Directed by Leo McCarey

Rufus T. Firefly is named president/dictator of bankrupt Freedonia and declares war on neighboring Sylvania over the love of wealthy Mrs. Teasdale.

Halfway through the famous Mirror Scene, Groucho knows that his reflection is Harpo in disguise, but it doesn't matter anymore, because the game has changed. The rules of the game are basically the same Calvinball, and there is no greater enemy than someone who is belligerently unwilling to join in the fun.

Will Sloan