A method and system for manipulating and mixing previously stored motion units for computer articulated figure animation. The motion units are combined in a weighted average. The weights give a priority to certain joint rotations of a motion unit which constitute the essence of that motion unit. The motion units can be mixed in an asynchronous fashion, with no limit on the number of motion units that can be mixed together. Phrasing control assigns a weight to each frame in a motion unit, and eases the transitions at the beginning and end of a motion unit. Frame-to-frame smoothing is also used. Fatigue of an articulated figure is simulated by the addition of a "tired" motion unit.