Why Animators Avoid Symmetrical Poses

Mickey Mouse from "The Illusion of Life"

One of the most common mistakes made by junior animators is for their character poses to be too stiff and symmetrical.  One of the fastest ways to make a character feel stiff and lifeless is to pose them symmetrically.  

Perfectly mirrored limbs, identical angles, and evenly balanced weight all scream “mannequin,” not “living being.” Real life — and good animation — is full of asymmetry.