Squash and stretch is very important in facial animation, not only for showing the flexibility of the flesh and muscle, but also for showing the
relationship of between the parts of the face. When a face smiles broadly, the comers of the mouth push up into the cheeks. The cheeks squash and push up into the eyes, making the eyes squint, which brings down the eyebrows and stretches the forehead. When the face adopts a surprised expression, the mouth opens, stretching down the cheeks. The wide open eyes push the eyebrows up, squashing and wrinkling the forehead.
The squashed position depicts the form either flattened out by an external pressure or constricted by its own power. The stretched position always shows the same form in a very extended condition.