A better explanation of just what this is can be found written by Paul over at House To Astonish:
This has been floating around on YouTube for a month now, going viral in other countries and waiting to do something in the UK. I’ve seen people comparing this to “Gangnam Style”, which misses the point, really. ”Gangnam Style” was a proper record which went viral in large part because the added dimension of incomprehensibility provided by a language barrier and a very specific set of cultural references. ”The Fox”, on the other hand, is a perfectly intelligible comedy sketch which wasn’t even intended for release – it’s a trailer for a Norwegian TV show (hence the time and date at the end of the video). Ylvis are brothers, and are apparently pretty well established in their home country. If this track sounds surprisingly professional for a novelty song, that’s because it’s produced by Stargate, which itself is meant to be part of the joke. Ylvis do a lot of parody songs on their showsThat very much explains everything. So in the United States this duo has likely been seen as something quite different than the intention for their original audience.