The pull of gravity is one of the most important principles to deal with in animation. Everything has a certain amount of weight and will act and react accordingly. One easy way to lose the attention of an audience is to have feathers falling like bricks or bricks falling like feathers.
A certain humor can be gotten by bending the rules but should only be used where humor or special effect is called for. In shorts cartoons defying the laws of gravity, weight, speed, squash and stretch, etc., is a the rule of thumb. In Disney feature cartoons such flamboyant abandonment must be handled more discriminately.