Portrait art is an interesting thing. Unfortunately it's not really something that's emphasized in many drawing and animation classes I've been in. I think that's because it's very different then what the focus of many animation drawing classes is. Animation classes don't tend to emphasize the element of capturing the likeness of particular people. They tend to be focused on things like understanding shape, line, and contrast which of course are wonderful. On the other hand I think there are things in portrait art that could really help all of us aspiring character designers. Good portrait art requires probing the sitters likeness and getting sometimes intangible elements of their personality into the drawing. That's something that can really be applied to animation design.