They should have more than four limbs. Four limbs are boring and uninteresting; nearly all vertebrates have four limbs, and they are largely a boring group of life. Arthropods have six or more limbs, and are far more interesting.
Terrowin Avatar by HappyTurtle. Much thanks!
I have a point!
I don't use the Registry; ask for a description if you don't know what my character looks like.