"Underdog," a new film by Swedish directer Ronnie Sandahl, comes with a fair amount of hype, after winning a variety of awards, including the Critics Choice at the 2014 Zurich Film Festival. However, when the film opens in Sandahl's home country later this month, as Swedish Web site the Local notes, some people are expecting the film to cause some controversy.

Why exactly? Well, consider a line in the trailer above: “My life is so much better now when I get my coffee served to me in the morning by a Swede," one Norwegian character says. "And when I take a s---, I know there's a Swede to clean it up for me.”

In response, a Swedish character bats back: ”[We Swedes] just see you as mentally disabled cousins who have won the lottery."

Animosity between the Nordic neighbors shouldn't be entirely unexpected – the two countries have enjoyed a long and complicated history. Both were once part of the Kalmar Union, which, at its peak, included Denmark, Finland and Iceland, too, and after a brief war in 1814, Sweden and Norway shared a monarch for almost a century, with a Sweden-based king controlling the foreign relations of Norway. The two countries only split in 1905.

More recently, there's the issue of World War II, when Norway was occupied by Nazi Germany, and Sweden was officially neutral; a historical fact referenced in the clip above: “During the war the Swedes were just standing there bowing to the Germans like prostitutes."

But mostly, relations between the two countries have been pretty good. They share not only geography and history, but also mutually intelligible languages and a somewhat similar Scandinavian outlook on life.

Sweden has, however, been the more prominent neighbor in the pair. With almost twice the population, it tended to dominate the cultural life in Norway and take up more space on the international stage. For a long time, it was the success story: In the post-war years, Sweden's relatively unscathed infrastructure allowed the economy to boom with companies, such as Volvo and Ikea, and Norwegians headed over to find jobs.

What "Underdog" examines, however, is how that relationship has changed. Sandahl's film focuses on the story of a 19-year-old Swede who travels to Oslo to find work and ends up working as a housekeeper for a wealthy Oslo family. It's a story familiar to many in both countries: Over the past few decades, Swedes have become unlikely economic migrants to Norway, with hundreds of thousands making the trip. One estimate from a few years ago said there were 50,000 Swedes just in Oslo, making up almost 10 percent of the population.

The reason for this change is simple: Oil. Norway discovered black gold in the North Sea in the late-1960s, and, after a few years of unprofitable investment, suddenly found itself making huge amounts of money from it. The Norwegian government created its own oil company, Statoil, and began putting away money into a sovereign wealth fund. By last year, there was enough money in this fund to provide $178,000 for every single one of the 5 million or so Norwegians.

Meanwhile, Sweden's economy struggled. Nowadays, GDP per capita stands at roughly $60,000 in Sweden, while it's at over $100,000 in Norway. The disparity in economies is so much that Swedes can go over and work in a cafe or bar and earn virtually double what they would get at home, while avoiding the high unemployment levels found in Sweden. It's not too different to economic migration from Eastern to Western Europe or even to the immigration situation in the Gulf States, but the close relations of the two nations and the relative affluence of Sweden makes it an unusual situation.

“When I was young, Swedes had whiter teeth, clearer skin, Abba and Bjorn Borg. We had lots of fish, and not much more,” Thomas Hylland Eriksen, a professor of social anthropology at the University of Oslo, told The New York Times in 2007. “Today, Swedes have been cut down to size [...] And I would say that many Norwegians enjoy the fact that so many Swedes are here doing menial jobs.”

It an interview with Variety, Sandahl explained why he felt he needed to make the film. "Now the Norwegians call us the 'paki-swedes' or the 'new poles,' the immigrant workers," he explained. "But the weird thing is that even though it is the biggest Swedish emigration in modern time – bigger than the boats to America in the late 1800’s – you don’t hear about it on the news, you don’t read about it."

Of course, now it's immortalized in film, how much longer will this imbalanced relationship last? Like many oil producing companies, Norway was hit by the recent drop in prices, with Bloomberg reporting that as many as 40,000 jobs may be cut out of a total of 250,000 worldwide. People are beginning to wonder what, exactly, Norway will look like after oil.