Zelig

Set in the 1920s and 1930s, the film focuses on Leonard Zelig (Woody Allen), a nondescript man who has the ability to transform his appearance to that of the people who surround him. He is first observed at a party by F. Scott Fitzgerald, who notes that Zelig related to the affluent guests in a refined Boston accent and shared their Republican sympathies, but while in the kitchen with the servants, he adopted a coarser tone and seemed to be more of a Democrat. He soon gains international fame as a "human chameleon". Read more on Wikipedia.