AJ, Rodney, and Theodore are not three different characters, but rather one.
Theodore is the proxy for AJ and Rodney, having split personalities for both of his most common moods. It is uncommon to find AJ and Rodney in the both place at the same time, IE, Theodore.
Rodney is not necessarily Mary-Sue, but Happy-Go-Lucky. He helps whenever he can, and always stops to say "Hi!". His attitude can be one related to Pinkie Pie. AJ always wears a pair of sweats and a jacket. He doesn't wear anything underneath.. Because why?
Rodney is a major asshole to everyone he meets. He won't think twice about punching a child in a face, and blowing smoke into peoples faces. He isn't far from using guns to commit robbery, and is a real douchebag, The only person he could get along with, is himself.