Check out this amazing software designed by Disney which enables character shapes and their desired motions to be generated very quickly.
From the video description:
We propose an interactive design system for rapid crafting of planar mechanical characters. Our method combines the simplicity of sketch-based modeling with the ease of defining motion through extreme poses. In order to translate these digital designs into fabrication-ready descriptions, our method automatically computes the mechanical structure that makes the characters move as desired. We achieve real-time performance by limiting the mechanical structure between pairs of components to simple building blocks that define, trim, and propagate their motion. By focusing on shape and motion, our system emphasizes the creative aspects of character design while hiding away the intricacies of the underlying mechanical structure. We demonstrate the flexibility of our approach on a set of virtual designs and physical prototypes.
By paring things down to just a character's outline and motion, the program is able to quickly generate 2D prototypes that focus on the underlying mechanical structure. The third dimension (depth) and aesthetic considerations can come later and benefit from a different set of tools. I like what they've done here. Linkages can produce some astonishing output motions from some simple inputs. Figuring out these linkages is far from intuitive however.
Here is where you can learn more about ChaCra: An Interactive Design System for Rapid Character Crafting.
[ Thanks Seth! ]