From the San Francisco Museum of Modern Art, this short video provides a small insight into how William Kentridge produces his amazing stop-motion films. (For an example of the finished product, see this vimeo film by art21.org).
Kentridge draws on paper with charcoal, takes a few shots, then erases parts of his drawing and draws over it again, and so on, until the scene is complete. The “finished”, palimpsest-like drawings are often displayed alongside the completed film. What an amazing mind he must have.