Few elements of Mad Men receive more regular scrutiny than the choice of final music that the show's creative team puts over the final credits of each episode. Each selection is assumed to hold a deep message about a character, the episode just concluded or the series itself.
How, then, did everyone miss this one?
"The Quality of Mercy" (the MASH ep) closes with a trippy, psychedelic anthem called the "Porpoise Song" by the Monkees. The song fits the late-60s setting of Mad Men's 6th season and the slight unreality that has crept into the series in recent seasons. Some commentators have also noted the "pre-fab" nature of the Monkees, and how their essential falseness might reflect Don Draper.
But none of that is why the producers picked it.
"Porpoise Song" is from one of the Monkees' movies, "Head," where it plays in the opening sequence.
Quick: think about Mad Men's iconic opening sequence. Got it?
Here's "Porpoise Song" in the opening of "Head."