Plushie workouts have nothing to do with building muscle or diminishing fat. Plushie workouts are aimed solely at redistributing stuffing. Being cuddled, hugged and carried all over creation by a loving individual often plays havoc with original stuffing placement. Proper exercise can shift squished stuffing back into place, thus avoiding flattened torsos or overstuffed arms or legs or even flattened faces. Only in extreme case is cosmetic surgery actually called for in the form of added stuffing. Exposed seams are always a risk and should be avoided if simple exercise can do the job less invasively.
See Woody's pre-kidnapping and post rescue physique changes in Toy Story Two for reference.
Plushie workouts have nothing to do with building muscle or diminishing fat. Plushie workouts are ai