Last weekend, a DJ caused a stir in Britain after playing the hit Wham! song "Last Christmas" at a soccer game in front of about 60,000 people.

A week earlier, another DJ had done the same at a match with 7,000 people, prompting him to apologize in an interview with the BBC.

Why? These tune-slingers had just "whammed" their audience, potentially knocking tens of thousands of people out of a long-running Christmas game.

Confused? Let's back up.

There is a game called Whamaggedon that's popular this time of year — especially in Britain — which consists of not listening to the holiday classic by the '80s pop duo.

From Dec 1-24, if you listen and recognize the original version of the song, it's game over. Listening to remixes and covers is fine.

"The very moment you have that 'Oh no' feeling in your brain, that's the moment you're out," said Thomas Mertz, who lives in Copenhagen, Denmark, and created the game almost two decades ago with some friends.

It's all for fun, there are no prizes, and if you do get "whammed," as Mertz called it, you just drop out.

Mertz made it clear that the song isn't the problem. In fact, he plays it repeatedly the week before the game starts, and again as a sort of celebration after he gets whammed. But he said in the early 2000s in Denmark, you pretty much couldn't go anywhere without hearing those dulcet tones.

"We were thinking, like, it's frustrating and it's getting to the point of being annoying. But rather than becoming upset about it, we turned it into a game," he said.

The challenge eventually became a hashtag and a Facebook page. It also blew up when Wham! lead singer George Michael died in 2016.

"That created a social storm of attention that the next year kind of launched it into a much, much bigger thing than we ever imagined it could become," Mertz said.

As for tactics, Mertz said he has seen two methods to avoid losing.

"The most effective thing is what people already have, which is noise-canceling headphones," he said. "They are the best tool, hands down, to survive."

A little bit of obliviousness also helps: "A lot of people tell me that they are the kind of people who kind of go through life a little bit oblivious to their surroundings, and they have an easier time of it than most, I think, because they just don't pick up on music."

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In Britain, some pubs have even taken the song out of their Christmas playlists, so as to not ruin the game for people. But the whole point of the game is that there is a risk of listening to the song, Mertz said.

So for those who are still in the game, best of luck. For those who are already knocked out, or just want a bit of Wham! magic this holiday season, have another spin of the Christmas classic.