Mad Men star Vincent Kartheiser stopped by the Rolling Stone studio recently to chat about the evolution of his character, the high-strung ad man Pete Campbell. "He found his place in the world," says Kartheiser. "He knows where he fits, he knows where he has value at the agency, and it's something you need to figure out as a human being, because you will be in constant conflict if you don't. In seasons one and two, he thought he should be where Don [Draper] was, and in seasons three and four, he kind of figured it out." Kartheiser also explains that he has no interest in directing an episode of the series, as his co-stars Jon Hamm and John Slattery have done: "I'm just an actor. I'm very much kind of a one-trick pony and hardly even understand my own character, much less the entire theme of the show."