Forgotten Silver, possibly Peter Jackson's best film. Sweet, sly, brilliant mockumentary about Colin MacKenzie, an unknown and entirely fictitious New Zealand filmmaker who invented the feature film, the talkie, color footage, and (my favorite) the tracking shot.
The Wizard of Speed and Time. Animator Mike Jittlov worked for Disney in the seventies and had hellacious experiences, including wrangles with an evil producer who refused to pay for Mike's work. So Mike made a modest feature film about it, playing himself. The film's producer played the evil producer in the movie -- and in real life; the climax came when he sold the video rights to several fly-by-night distributors simultaneously, inextricably tangling the rights and ensuring that nobody would ever see a dime. Jittlov refers to the product as the Nostradamus of motion pictures -- but it's a fun, cheery movie with great music and hand-animated special effects.