Danes and Norwegians were part of the same country for hundreds of years, and they’re still family.  Written Danish and written Norwegian are very similar – so similar that I once tried to find a Danish-Norwegian dictionary and was told there was no such thing.  The spoken language is a little more different, but still Danes and Norwegians can understand what the other is saying.  
Danes and Norwegians like each other.  They care about each other.  They even sometimes cheer for each other’s football teams.
But like any family, there’s envy involved. Envy.

For example, there’s envy of each other’s geographical pleasures.  Norway has beautiful mountains, great for skiing.  Denmark has windswept beaches, which the Norwegians seem to love. Lots of summer holidays in Denmark.  
The real envy, of course, is about money. Norway has money, because of North Sea oil. 
There is a feeling among some Danes that some of that oil should have been Danish oil. During a meeting to divide up the waters between the two countries in 1963, the Danish negotiator, Per Haakerup was photographed with a glass of whisky in his hand.
The rumor is he was drunk during the meeting, and gave up the Ekofisk oilfield to Norway, which has earned billions of dollars from it.