Larry David (the character) is a keen observer of social custom and human behavior. He doesn't quite fit into society, however, and many of Curb Your Enthusiasm's shenanigans occur because Larry consistently acts abnormally and/or breaks the rules of social custom.
Dexter Morgan is also a keen observer of social custom and human behavior. He has to be: he's a serial killer lacking human emotion, and so he must fake normality. He can act according to the rules of social custom, and general appear to be a normal human being, because he works so hard at faking it.