John Slattery, 'My Old Kentucky Home' (Season 3, Episode 3)
In what's surely one of the show's most uncomfortable scenes, Roger Sterling (John Slattery) dons blackface and sings "My Old Kentucky Home" at a Kentucky Derby party. As Weiner told Vulture, "that episode is about white people and what they're like when they’re alone" — in this case, donning shoe polish for a little casual racism. Slattery also noted in an interview after the fact that "it's horribly offensive, obviously, but this is the point. This is where we were. It was so commonplace. This is the message, and Roger's the messenger." Not even Pete and Trudy dancing the Charleston later on can lighten the mood after that display.