[neverending]

These are actual double features I've seen in theatres, and the entertainment value of each was extremely high:

The Adventures of Robin Hood (Errol Flynn) - Robin & Marian

Casablanca - Play It Again Sam

The Casablanca/Sam pairing is particularly effective as Play It Again Sam opens with Woody Allen watching Casablance in a theatre, and as the end of the film rolls past, Woody's mouth slowly drops down in awe in reaction to the amazing film before him. It's a superb example of art imitating life as you realize YOU the viewer just did the same thing as you watched the end of Casablanca....