In Mad Men, Don Draper has a troubled past: he grew up very poor, enlisted in the Korean War, and
stole the name and identity of an officer he served under.
However, the first hints of his concealing his past did not come until the second episode of the first season, when he deflects from a conversation about childhood while having dinner with Betty and the Sterlings. (The pilot episode does establish that he served in Korea, saw combat, and was awarded a Purple Heart.)
My understanding is that seven years passed between Matthew Weiner writing the first draft of the pilot and the show getting picked up. At what point in the process did Don Draper’s mysterious past get fleshed out? Was it all Weiner’s idea, or was it a collaboration between him and others?