Warning: This story discusses the series finale of Mad Men. Beware of spoilers.

Just days after Mad Men aired its widely praised final episode, creator Matthew Weiner is opening up about that Coke ad that closed out the show's epic run.

In the episode, which aired Sunday, Don Draper found himself experiencing an emotional breakthrough while on a hippie retreat — which, fun fact: was filmed in Big Sur. The closing moments of the series showed Don meditating then breaking out into a coy smirk before cutting to the vintage "I'd Like to Buy the World a Coke" ad.

"In the abstract, I did think, 'Why not just end the show with the greatest commercial ever made?" the writer told a crowd during an interview at the New York Public Library Wednesday. "In terms of what it means to people...it was nice to sort of have your cake and eat it too in terms of 'What is advertising?' [and] 'Who is Don?'"

So yes, it seems, Don did write the ad. Sorry, Peggy fans.

"And the idea that some enlightened state — and not just co-option — would have created something pure" was an appealing idea, he added, responding directly to those who criticize the ad as being "corny."

"That ad to me is the best ad ever made and comes from a very good place — which is a desire to sell Coca Cola probably," he joked.

Weiner, who maintains that "no money changed hands" between the show and the soda company in exchange for the shill, even screened the ad for Kiernan Shipka, who played Don and Betty's daughter on the series, to test her reaction. The result?

"She was like, 'That song is so beautiful. I don't think there are people with faces that pure on TV anymore,'" he said.

Weiner, meanwhile, claims he'd known how he was going to end the series since Season 4, after the cast signed new contracts with the show. That's also around the time he decided Betty would be diagnosed with terminal cancer.

"In the back of my mind, I knew about the Coke ad. At that point I knew about Betty dying; I did not know about Peggy and Stan," he said, referring to the start of the fan-pleasing relationship. "That had to be proved to me."

You can watch his whole interview below:

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