1983 animation test by Disney, directed by John Lasseter (who went on to direct and produce most of the Pixar films, including Toy Story). Back then Disney owned the film rights to the Where The Wild Things Are books... they didn't use them, though, so they lost them. Check out this amazing test, which combined traditional hand-drawn, 2D animation with then-state-of-the-ar t 3D computer animation!
