Jad's right about the torso twisting. And have you thought about how cool the cool walk would be if he snapped his fingers on the ascending motion of each arm? @u@
Your characters have very appealing design but there's a little pillowing and weak shading going on which doesn't let the designs amount to all they could. They're also a little bit under-saturated. Desaturation isn't a bad thing, but it can be when it means the contrast suffers. I made a quick edit which appeals to my own tastes a little more in terms of color, but it also helps the clarity.
Consisting of: bumping up the the overall contrast followed by the darkening of that gray shadow you use on the hair, and then trying to remove "islands" of colors by making the islands extend to touch the outlines, and preferably be surrounded by other colors on the least number of sides, not including outlines. The outline of the hair was messy so I attempted to clean it up. I tried to eliminate single pixel lines of shadows along the outlines. The two pixel abyss between the legs wasn't really helping much, it wasn't making the legs seem like they had any curve inwards, so I got rid of it.
There are other minor instances of pillow shading on Mortimer Cool's pants, search and destroy! Your designs will come to life much more effectively than they already do when the shapes read clearly and distinctly without being muddied by useless shading. If this were another medium, I suppose "form bending" shadow would apply to those areas, but because this kind of pixel art is indexed, you don't really have the luxury of soft gradients, not to mention at this size it merely hurts the crisp distinct shapes that are important for optimum readability.
If Helm were writing this he would probably say something about claustrophobic pixel clusters. So let them breathe and have nice large clusters of uninterrupted delicious pixels!