In this seven-minute video, Walt Disney describes the MultiPlane camera. Invented by William Garity for Walt Disney Studios, the camera allows photography of multiple layers of film, with control over the relative movement of each layer. This allows for more realistic control of things like zoom-ins -- it's sort of "3D-ish," at least for cel animation.
Worth a look for anyone interested in animation, technology, or photography. My favorite part is around 6 minutes in, when two clearly dubbed camera operators talk through a technical problem. Boy, that scene was swell.