Personality is unique for all human beings and they should not be classified. Although human's personality can not be classified, the personality theories from psychologists are useful for people. It is because we can know much about people's thinking through studying the personality theories or taking the personality quizzes.
This comic makes me think of the double personality of some people. I think people with double personality is very mysterious because you won't know how is his or her real feeling or opinion. It is quite interesting and I think I should do more research about it.