This is a fairly recent development. When I moved to Sweden in the 1970s, it was so bad I learned Swedish at accelerated rate in order to avoid the kneejerk compulsion of many (if not most) Swedes to tell their favorite jokes about how dumb Norwegians seemed to be. No doubt a consequence of century-old rivalry and the fact that Sweden during the early part of the last century was the larger, richer, most industrialized and organized society in comparison. And they believed much of it to be actually true, in the way that derogatory humor always evokes some degree of "no smoke without fire." To this day, I meet swedes who are surprised at hearing that bananas are not actually called "gulebøj" in Norway (bended yellow) - a reference to how Norwegian is not as anglicized as Swedish, as there has been a pushback against this trend in Norway historically. As Norway has become progressively richer these jokes in Sweden about Norwgians have more or less disappeared however.

The notion that Norwegians nowadays have the same jokes about Swedes is something I hear repeated, but it saddens me nonetheless because it doesn't rhyme with the spirit I remember from my childhood. If true, then it means that a fair number of my present (Swedish) countrymen are being denigrated, perhaps because Norway can now pride themselves on being the richest (real) country in the world per capita, so rich that a lot of swedes migrate here to take the worst paid jobs in restaurants and in hospitals. They are popular as employees because they understand the language and are hard working. And probably because they can take denigrating jokes, maybe because well, they used to do it too. But it's not all that funny, really.