[I've always thought of Pitt as a snake but I ACCEPT your characterization of him as a "cameleon." (Is that a camel that can change colors?)]
You're both on the right track...the rare WRPitt Viper, recognized by its beady eyes, forked tongue, and ever-changing camoflauge as it tries to fit in to a particular setting; known by its repeated attempts to set itself up as an expert in any given field, its namedropping habits, and its flamboyant displays before a camera lens.
With Chris "Son of Mama T" Heinz...With Joe "Mr. Valerie Plame" Wilson...With John "DSM" Conyers