5. "Shut The Door, Have a Seat" (Season 3, Episode 13)
The most bizarrely upbeat Mad Men episode, which means it probably shouldn't count as a Mad Men episode at all. It's practically a caper movie: The Sterling Cooper crew hatch a scheme to break free from their British bosses and start their own agency. It's full of team-spirit comic camaraderie. (Besides the scenes where Don and Betty give their marriage those last few fatal clubs to the jaw.) When Roger announces, "Mrs. Harris, what a pleasure to see you," it's like she's Han Solo zooming in at the last minute to rescue Luke Skywalker. And Lane crowing "Very good, happy Christmas" on the phone is probably the giddiest moment of his life. Oh, Paul Kinsey — we feel your pain.
Best line: "I was going to tell you. No, I wasn't."—Roger Sterling