Yugoslavia isn't known as a mecca of horror media, but we do have at least one classic to thank it for. John Landis was working in a Central European country during the making of Kelly's Heroes. While working as a production assistant, the future director would encounter a burial ritual that would inspire An American Werewolf In London. 

In Giulia D'Agnolo Vallan's 2008 book, John Landis, Landis discusses how the movie came to him some 10 years before it even entered pre-production.

"I wrote it during Kelly's Heroes. And that piece I wrote about the funeral is absolutely true, that's what happened. Because we thought it was funny at the time, but if it had been real, how would we have dealt with it? For a sophisticated person, the premise of the supernatural is unacceptable— werewolf, zombie, vampire, whatever. It's preposterous!" 

But what of that funeral? How did a Romani tradition come to influence one of the most beloved horror-comedies of all time?

Luckily, D'Agnolo Vallan also included Landis' recollection of the incident and how it deeply affected his later work.

"A crossroads, around thirty people milling about. Sasha standing to one side. I went to stand by him. 'What is that?' It's a body wrapped in canvas with garlic strung around it and, yes, those are rosaries. Two men digging in the road at the crux of the crossroads as a Greek Orthodox priest waits. Tall hat, long beard, yes, I'm sure he's a priest. The others are [Romani[. I know this because they look and dress like [people of Romani descent]. The whole scene was straight out of a Universal back lot."

The dead man had apparently committed some crime and was buried in such a manner as to prevent his unholy resurrection. That event, plus the presence of a full moon that evening, set Landis' mind in motion. The rest is horror history!