16. "5G" (Season 1, Episode 5)
All men have secrets, as a wise man once sang. Don is a man who's made of secrets — whether that means a beatnik girlfriend in the Village ("I want you to pull my hair and ravage me and leave me for dead") or a family photo burned to ashes in the wastebasket. Like Joan says, "Private…that's how these men are. And it's why we love them." But Don's darkest secret threatens to blow up when he gets a visitor from his previous life. His long-lost brother Adam shows up at the office, asking what everyone wants to know: "Who is Donald Draper?"
Best line: "I'd like to see more of it around here — people finishing things. I guarantee you that in the bottom drawer of every desk in this place is the first 10 pages of a novel."—Roger Sterling