Balance in a key pose is important. It is important for the visual communication of believability between the animator and the viewer through the character. Otherwise the viewer will sense that something aint quite right and not find appeal in the animation. Yep, the animation principle of Appeal.
Balance, Line of Action, Psychological Gestures, Meaningful Symbolism all form a part of posing. Posing can be thought of within the animation principle of Solid Drawing. But it also features, by name, in the principle of Animation Type, when talking about Pose-to-Pose animation.
Balance is influenced by gravity. Gravity does not automatically exist on a piece of paper or in animation software. So an animator has to practice with gravity some other way to work out how to show it in animation. One way is to "Act It Out".
The other way is to pose a character who is influenced by gravity. Introducing "Yellow". (I think the pose below is the pose Jess - 2nd Yr - created).
If the computer screen has fraznicked your thinking, spend some refresh time posing "Yellow". He resides inside the digital camera box.
Yellow appears on some second year blogs already: Sarah P (the first one to achieve balance on one leg) and Cassie V.
Workplace health and safety warning notice: 1 leg poses should only be attempted by 2nd years. Do not attempt to act out poses found on these blogs at home without clearance from your physiotherapist.