Have you ever known a chameleon person?

NOT someone who changes colors, LOL but either of the two types: (1) changes clothing, attitudes, hairstyle, etc, to fit whatever is popular or cool at the moment. (2) changes opinions and actions to fool people around him/her into thinking s/he is a nice person and is on their side. I've know both and they are awful! So insincere. What did you think of your chameleon person? Do these folks have no personalities of their own? Why do they do it?