Sunday's Mad Men touched on many recurring themes for the show: sex, degradation, how we present ourselves, what marriage means, how we commodify affection. Pete tried to convince Joan that she'd be like Cleopatra; the scuzzy Jaguar guy said he felt like Ali Baba looking at Helen of Troy. ("Those are different stories," Joan said. Get it?) But there was another, more subtle call-back in the episode. Joan wore a familiar fur to meet that sleazy Jaguar guy: It's the chic number Roger gave her, right when they first started dating, back when Don Draper was just some guy who was hoping Roger would give him a job.
Prostitution has always been part of the Mad Men fabric: Don's dead mother was a prostitute. Betty's mother called her a prostitute when she started modeling. Betty's old roommate is a "party girl," which Don gently explains in "For Those Who Think Young." The SCDP guys have procured "girls" for clients on many occasions, starting in the first season. We know Don enjoys having a prostitute slap him around. We've also seen characters trade on sex and sexuality, and we've seen Roger ask Joan to wear specific outfits to entice specific clients, and have seen Don scold Sal for not just giving in to a client's advances.
Joan's fur coat makes its first appearance in season four's "Waldorf Stories," the episode where Don gets incredibly drunk at the awards show. "We've all had nights in our lives where we've made mistakes for free," Pete tells Joan in this week's "The Other Woman." No kidding.