Pyeongchang (CNN) Sport is built on great rivalries and perhaps greatness cannot truly be achieved without the presence of a nemesis.

There's Roger Federer versus Rafael Nadal, Real Madrid versus Barcelona, the Yankees versus the Red Sox -- and then there's Sweden versus Norway in cross-country skiing.

Which explains why Swedish reporters are attending a Norwegian press conference in a nondescript gymnasium in Pyeongchang.

Not that they've come to listen to what Norway's cross-country skiers, the best in the world in this punishing trade, have to say. Instead they have a trick up their sleeve, a prank which will later spark numerous articles and copious amounts of TV coverage in the two neighboring countries.

The journalists from Swedish newspaper Expressen have brought with them a cardboard cut-out of Norwegian cross-country great Petter Northug. This is not a spur-of-the-moment piece of mischief, the Northug cutout flew with the Expressen team from Sweden to South Korea.

Why? The two-time Olympic champion was not selected by the Norwegians for the Winter Olympics, but the 32-year-old is a figure the Swedes love to hate.

Swedish fans wanted Northug at PyeongChang 2018 and so their journalists brought the next best thing with them to the Games and placed the one-dimensional Northug in front of the microphones. Photographers clicked into action and TV crews filmed the comical scene before a Norwegian press officer took him away.

Sweden's feelings towards Petter Northug? It's complicated ...

'The Norwegian media loved it'

There's history when it comes to the Swedish-Norwegian cross-country cold war.

"Ten to 12 years ago a guy called Petter Northug rocked up, became the best in the world, and escalated this Sweden-Norway cross-country fight," Tomas Petersson, of Expressen, explains to CNN Sport.

The real Petter Northug

"He loved to win, but he loved even more to mock the Swedes and he's been doing it for 10-12 years. And this started the war in the media.

"Every time a Swedish journalist interviews Petter, he brings the hard stuff against Swedish skiers and Sweden in general.

"As a newspaper in Sweden we love Petter because he brings interest to the sport and what we write, so we brought a cut-out of him here.

"It was fun. The Norwegian leaders weren't so happy, but the skiers thought it was quite funny and the Norwegian media loved it. The article on that trick was the most read story in our newspaper that day."

Sketch of Petter Northug by @Channeldraw.

The Expressen team have another stunt planned before the conclusion of the Games, but Petersson smiles when probed to reveal more.

"It's a bit more sensitive so we don't know if we can pull it off," he says.

Norway's riposte to such high-jinx? By winning gold medals. Lots of them.

Of their table-topping 13 golds, six have been won in cross-country skiing. The Norwegians have, so far, won 13 of the 30 available medals in a sport that doubles as a national obsession.

Sweden -- second to Norway in the cross-country medal table in Sochi four years ago -- have five medals, two of them gold.

"We're getting pretty used to it," says Petersson wryly of Norway's success.

"Norway has been better for some years now. We get a bit tired of it."

Charlotte Kalla is one of the stars of Sweden's cross-country team, winning gold in Pyeongchang.

Over a hundred years of rivalry

To understand this battle for supremacy on the trails, we must go back to the 19th Century, to the 1880s when the two countries were in union, under the reign of one monarch. There was political conflict and rumblings of war before the coalition was peacefully dissolved in 1905.

"Sport in Norway was organized in the 1880s as a kind of war preparation against Sweden," explains Esten O. Sæther, a journalist for the Norwegian newspaper Dagbladet.

"Our sport association was founded in order to prepare to tackle the Swedish. Luckily, there wasn't a war, but since then it's been a struggle between Sweden and Norway and, mostly, a friendly struggle, and the most important sports struggle has been in cross-country skiing."

Northug is a two-time Olympic champion.

Thirty years of hurt for Sweden

Sweden was the dominant force in cross-country skiing in the 1980s, but then came the Norwegians, on a mission to rule the snow world.

Before hosting the Winter Olympics in Lillehammer in 1994, the Norwegians established the Olympiatoppen, their national elite sports center, and the result has been over 20 years of dominance in cross-country skiing.

At these Games, that success has broadened to other sports and the Norwegians have celebrated glory in Alpine skiing, biathlon, curling, freestyle skiing, ski jumping and speed skating.

But it is cross-country skiing, and beating their Swedish neighbors, that matters most to this country of 5.2 million people. Sweden's population is nearly twice the size of Norway's.

Their supremacy in their national sport is not all of their own doing, however. Norway has been assisted, says Sæther, by the Swedish population's shift from the countryside to the cities during the 1950s and 60s.

Norway's Ingvild Flugstad Oestberg, Astrid Uhrenholdt Jacobsen, Ragnhild Haga and Marit Bjeorgen pose on the podium during the medal ceremony for the cross country women's 4x5km relay.

Johannes Hoesflot Klaebo celebrates after Norway win men's 4x10km relay in Pyeongchang.

While interest in cross-country skiing remains high in Sweden, the number of participants in the sport is dwarfed by Norway.

In Sweden's national cross-country championships, says Sæther, there will be roughly 70 competitors in the men's and women's events. Across the border, there will be 250 athletes vying for national supremacy.

"Every child has a pair of skis and it's very common on Saturdays and Sundays to go skiing all over the country in Norway," says Sæther.

"It used to be the same in Sweden, but the main difference is that in Sweden the people moved earlier to the cities.

"They lost a lot of the population in the rural districts and the best skiers usually, or used to be, from rural districts and it's still like that in Norway.

"When you have a great part of the population in the cities then you could have a problem."

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Doping bans, souring of relations

It could be argued that no sporting success story can compare to that of Norway's in cross-country skiing.

This snow nation has won 18 medals in total -- including gold in all five of the women's events -- at the 2017 World Championships in Finland, seven more than nearest rivals Germany.

It is Norwegians - Heidi Weng and Johannes Hoesflot Klaebo -- who lead the current overall World Cup women's and men's standings.

In recent years questions have been raised over the ethical use of asthma medicines by Norwegian athletes.

Recent doping bans for Norway's Martin Johnsrud Sundby and Therese Johaug means the Norway-Sweden rivalry has not always been good-humored.

Sundby was banned in 2016 for over-use of an asthma medicine, while three-time Olympic medalist Johaug tested positive in September 2016 for the steroid clostebol.

Johaug, now 29, said the positive test came from the use of an ointment used to treat sunburnt lips during a training camp.

An investigation by the Norwegian Ski Federation found no wrongdoing by the team, but the 191-page report did say that the use of asthma medicines to treat temporary symptoms represented an ethical dilemma.

Sæther says: "You had a poll two years ago that shows about 40% of the Swedish population think that it's organized doping in Norwegian cross-country. That was a big story. It's the media that are raising the suspicion. It's the harsh language they use."

But Expressen's Petersson says he and his compatriots are reporting Norwegian doping stories just as any other country would.

"Of course, if Norwegians are accused of cheating then we write about it," he says. "In both cases it was unlucky. I don't think they were cheating on purpose but they got caught."

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Who cares the most?

Despite recent controversies, this still remains one of sport's friendliest, and often entertaining, rivalries.

Which country cares the most? The answer depends on the nationality of the narrator.

"I was in the world championship in Sweden in 1993 and at that time Sweden was really bad," says Sæther.

"I was walking behind a small boy one morning and I heard him say to his mother 'I hate Norwegians, I really hate Norwegians' because they're winning everything.

"It's quite hard when you're so interested in cross country and you lose almost every time."

Marit Bjoergen crosses the finish line to win gold with Ingvild Flugstad Oestberg in the women's 4x5km Relay

But Petersson describes the relationship akin to that of siblings. Norway, the smaller, younger brother, obsessing over the big brother.

When the Expressen columnist wrote an article before the start of the Games, claiming that he did not think Norway's Marit Bjoergen would reign supreme in Pyeongchang (the 37-year-old cemented her place as the greatest ever Winter Olympian with a relay bronze medal on Wednesday), within 90 minutes he had received over 300 emails from irate Norwegians.

"Everyone was pissed with me," he says. "Sweden is like the bigger country and have influenced Norway a lot. They've always been interested in anything that happens in Sweden so they love being better than Sweden in sports.

"The Swedes don't care that much. But it's really fun and brings a lot of interest to the sport. It's really something special."