Here are two images showing squash and stretch of a human face.
One is clearly hand-drawn and one is clearly computer-generated. The hand-drawn one is much more appealing, but why? The cgi one is unappealing because the entire face is squashed and stretched uniformly with a lattice while the hand drawn one keeps certain features (the eyes, nose, and mouth) the same size but still spreads them out along the overall stretched head shape.
With some clever tricks we can have parts of a mesh deform rigidly within an overall lattice deformation. This is just a technical tutorial on the technique that you can use to achieve results like that.