Duck Soup

The 1933 movie Duck Soup is about the closest we've come to a perfect comedy. It stars the four Marx Brothers plus Margaret Dumont. It was Zeppo's final film with his brothers. The synopsis:

Groucho portrays the newly installed president of the mythical country of Freedonia. Zeppo is his secretary, while Chico and Harpo are spies for the neighboring country of Sylvania. Relations between Groucho and the Sylvanian ambassador deteriorate during the film, and they go to war at the conclusion.

Even if you've never seen the whole movie, you already know some of the highlights, like the hat exchange, the sidecar gag, and the famous mirror scene. Oh yeah, and a lot of jokes you've heard over the years. (via Metafilter)