Act the Part
During the production of an animated feature each animator will often be responsible for drawing just one or two characters. This allows the animator to get into the character in much the same way as a live action actor does. The more the animator can absorb themselves into the part the more convincing the character will be to the audience. Many animators enrol themselves for acting classes in order to improve their own acting skills.
Humans are particularly good at reading facial expressions. Animated characters expressions are often exaggerated slightly to add comedy value and to achieve great expressions animators find the best reference is their own face in a mirror.
