How an unexpected layover at Shannon Airport inspired one of the most famous ad campaigns ever.

As the AMC series "Mad Men" came to an end Sunday night after seven rich, wonderful and slightly drawn out seasons, a real TV advertisement from 1971 played across the screen.

We won’t give away any spoilers as to what it meant for "Mad Men’s" plot, but we were intrigued to find out a surprising Irish connection.

The ad, “I’d Like to Buy the World a Coke,” was one of the soft drink company’s most successful campaigns of all time. It was dreamt up by real-life ‘Mad Man’ Bill Backer, who, like the fictional Don Draper, was creative director on the Coca-Cola account for the McCann Erickson advertising agency.

As Coca-Cola shared on their website yesterday, the inspiration came to Backer in – where, of all places? – Ireland’s Shannon Airport.

Backer was flying to London to meet with Billy Davis (the music director for the Coca Cola account) and two British songwriters, Roger Cook and Roger Greenway. Heavy fog ahead in London forced the plane to make an emergency layover at Shannon. The passengers, who were forced to remain near the airport in case the fog lifted, were apparently less than happy with their accommodations.

But the next day, Backer was surprised to see many of the previously furious passengers sitting together in the café at Shannon Airport, sharing a meal and some Cokes. (For the sake of the story we won’t ask why they weren’t drinking Irish coffees when they were so near to the birthplace of Irish coffee.)

As Backer recalled:

"In that moment [I] saw a bottle of Coke in a whole new light... [I] began to see a bottle of Coca-Cola as more than a drink that refreshed a hundred million people a day in almost every corner of the globe. So [I] began to see the familiar words, 'Let's have a Coke,' as more than an invitation to pause for refreshment. They were actually a subtle way of saying, 'Let's keep each other company for a little while.' And [I] knew they were being said all over the world as [I] sat there in Ireland. So that was the basic idea: to see Coke not as it was originally designed to be – a liquid refresher – but as a tiny bit of commonality between all peoples, a universally liked formula that would help to keep them company for a few minutes."

We’d like to think Ireland had a little something to do with it, too!

Watch the full ad here, and an interview with Backer below.