From what I have seen on the PM style is:
I hope this all helps =D
- the ones with less animations get shading.
- there are two pixels on the outline, only on the outside.
- the colours are quite dull but saturation wise you have AA on the lines.
- the eyes have to little rectangles (there are some exceptions but only a few).
- and the anatomy depends on the character (like because Mario is a fat man, he has no legs, but for someone he is tall and slim he would have legs).
I hope this all helps =D