The thinking man’s nerd, Adam Brody so inhabited the charm of the neurotic Seth Cohen on “The O.C.” (Fox, 2003-07), that many believed he was simply playing a version of himself, so completely did he nail the character. Fans of both sexes admired the actor’s unmistakable cool vibe, but they also worshipped his knowledge of the underground music scene and comic books. The idea of “geek” suddenly became “chic,” with Brody the crown prince of a new idea of teen spirit. So beloved was the actor, that when he and his “O.C.” co-star Rachel Bilson broke up after a long-term courtship, there was a