The sequence where Peggy and Joey say "John"/"Marsha" to each other over and over is a reference to Stan Freberg's 1951 soap opera parody record, "John and Marsha"
Show creator Matt Weiner told interviewer Terry Gross that he included the detail of the "Advertising Age" reporter having a wooden leg because he was "basically hoping that on some subconscious level people would understand that this was Don's life - that what's left of his life is a phantom limb."
Don's date, Bethany, mentions the death of Andrew Goodman. This is a reference to the murders of three civil rights workers, James Earl Chaney, Andrew Goodman, and Michael Henry Schwerner in Philadelphia, Mississippi on June 21, 1964.
This episode picks up 11 months after the Season 3 finale.