Just CHEW the Scenery!

One of the traits that cartoons are known for is the exaggerated expressions. Daffy here is running in terror, obviously. Now, aside from the fact that ducks don't really run, or have hands, the main anatomical feature that is exaggerated is his mouth. No mouth--human or duck--can stretch that much. But that's one of the great things about cartoons: you can stretch and bend anatomy to heighten emotion.

This might seem restricted to the abstracted world of Looney Tunes or Disney. But the same principles can be applied to much more realistic styles of drawing. Though not to the extent of cartoon characters, realistic anatomy can be stretched or squashed to a minimal degree to communicate an idea. I've been applying this in my drawings recently, specifically with some Street Fighter sketch cards I've been working on. Here, Blanka's and Balrog's mouths are both open a little wider than the actual human mouth can stretch, and I pulled the lips at the corners a little further (theoretically adding muscles to the facial anatomy; I personally have some pretty flexible lips, and even I can't pull my mouth exactly like this). If you don't believe me, take a look at the reference photos I was using. Under close examination, you'll see what I'm talking about.

The purpose of this was to show some real rage in both characters. Bearing teeth is a worldwide human gesture to show anger: the more teeth you show, the angrier you can look.