Buster Keaton's Funniest Gag

In this scene from the 1921 movie Hard Luck, Buster Keaton misjudges a dive and crashes through the brickwork. It's a riff on the old joke about digging a hole so deep that you eventually reach China. Keaton said the gag got more laughs than any other in all his movies. However, the film was lost for many years until it was partially reconstructed in 1987- without the pool scene. That part was finally found in a Russian archive years later.

But how did he do that drive into the brickwork? Silent Locations explains that the pool did extend to the left, but was covered for the scene. Keaton often did dangerous stunts for his movies, but he couldn't dive that far out, so the falling scene was enhanced with animation cels of his body falling. You can see the entire movie here. (via reddit)