What was so absolutely mind-boggling about The Dark Crystal was how Jim Henson, Frank Oz, and the rest of the production team constructed the planet Thra and all of its denizens from scratch. From documentary aficionado BehindCurtain1, this is a 1982 behind-the-scenes documentary about the production (2, 3, 4), Check out how a fantasy world was constructed using practical effects.

[Via Nerdcore]