Squash and stretch also defines the rigidity of the material making up an object. When an object is squashed flat and stretches out drastically, it gives the sense that the object is made out of a soft, pliable material and vice versa. When the parts of an object are of different materials, they should respond differently: flexible parts should squash more and rigid parts less.
An object need not deform in order to squash and stretch. For instance, a hinged object like Luxo Jr. (from the film, Lv, xo Jr. I21]), squashes by folding over on itself, and stretches by extending out fully. (figure 3)