For a time, fans theorized that Sterling Cooper advertising agency in 1960s New York ( that name), but suffers an identity crisis when he is forced to confront his murky past. Revealed to be a child of the Great Depression, Draper (real name, Dick Whitman) was born into poverty, abused by a cruel step-mother, and eventually fought as a soldier in the Korean War. When Lieutenant Don Draper dies in an explosion, Whitman assumes his identity - keen to cut his service short and sever all ties to his previous life.
While it has since been debunked by showrunner Matthew Weiner, for a while Mad Men fans theorized that The Mystery of D. B. Cooper. It’s a fascinating case, with a number of potential suspects, and naturally lends itself to dramatization - offering plenty of knowledge-gaps for storytellers to plug with their own imaginative theories. In real-life, Cooper (almost certainly an alias), hijacked a Boeing 727, procured a ransom of $200,000, and parachuted to an unknown fate. These events occurred in 1971 but, to this day, the case has yet to be officially solved and was closed by the FBI in 2016, who decided that their resources and manpower would be better utilized by solving more pressing crimes.
Despite Weiner’s objections, the Don Draper/D. B. Cooper theory is actually pretty compelling and gained a decent amount of traction leading up to Mad Men's final season. Draper, like Cooper, has a history of switching identities and (the detectives assume, in Cooper’s case) military experience which may have allowed him to successfully parachute out of the plane and land, relatively unharmed. Draper’s personality and characteristics match those of witness descriptions given during the Cooper investigation: they’re both middle-aged, dress sharp, and drink bourbon, though Draper doesn’t resemble the composite sketch of Cooper later released by the FBI. That said, it is just a composite sketch, so the resemblance to Cooper in real-life is dubious. Additionally, Draper works at Sterling Cooper when the show begins, under Bert Cooper, providing an obvious answer for where the Cooper alias stems from.
Don Draper becoming D. B. Cooper would also make sense thematically, mirroring Mad Men’s established motifs - concerned, as it was, with fractured identities and recent American history. The show regularly covered historical events, blending fact and fiction in a way that resembles the eventual mythologization of the Cooper case. Mad Men even features a falling motif in its title sequence, which could have foreshadowed Cooper’s parachute jump.
When asked whether he was debunking the D. B. Cooper fan theory by Mad Men fans who are desperate to know what Draper might have been up to after the series ended - and an intriguing true-crime mystery that has yet to be solved.