Warning: There are spoilers ahead.
The series finale of "Mad Men" ended on the popular 1971 Coca-Cola ad, "I'd like to Buy the World a Coke."
While the ending may have left some wondering why that was the ad "Mad Men" ended on, diehard fans of the series will know the famous commercial was alluded to way back in season one.
In episode 9, "Shoot," Don Draper (Jon Hamm) takes then-wife Betty (January Jones) to the theater to see a show. During intermission, Betty speaks with Jim Hobart, the head of McCann Erickson.
While making small talk, Hobart mentions he's working on an international campaign for Coca-Cola and invites Betty to try out as a potential model given her resemblance to Grace Kelly.
Interested by the idea of returning to modeling, Betty takes Hobart up on his offer, trying out for the ad campaign.
However, Hobart's main interest in Betty is to try and steal Don away from Sterling-Cooper. Hobart sends over the images of Betty to Don, but the ad man isn't having any of it.
As a result, Betty doesn't end up on the Coca-Cola account.
Hobart shows up again in season 7, episode 2, "A Day's Work," trying to court Draper another time (not particularly for a Coca-Cola campaign).
The "Mad Men" finale brings the Coke storyline full circle.
At the end of the episode, the 1971 ad that plays was made by McCann Erickson, the agency Hobart worked for in season one.
Funny enough, the ad even ended up with two prominent blonde haired young women, similar in appearance to a young Betty Draper.
You can watch the ad below:
SEE ALSO: Here's the 1971 Coca-Cola ad that played during the "Mad Men" finale