19. "The Qualities of Mercy" (Season 6, Episode 12)
Child actors are a loser bet — you gamble a family drama on them, you usually end up stuck with an A.J. or Meadow. How the hell did Mad Men get so lucky finding Kiernan Shipka to play Sally Draper? How did they know she'd turn into a real actress? After Sally gets a revelation about the dark side of Don Draper, the same thing Dick Whitman learned about his own father — a dishonest man lives here — she flees to prep school and spends a hilarious night putting her dad's sales expertise to work on the mean girls of Miss Porter's School.
Best song: The Monkees' "Porpoise Song," playing in Don's head as he curls up on the couch, a dirge for all the second chances he's blown.
Best line: "My father has never given me anything."—Sally Draper