[ochrist]

There are a few facts you should know about this:

Formally Norwegian is West-Scandinavian (together with Icelandic and Faeroese), whereas Danish and Swedish are East-Scandinavian.

Also, please remember that the Norwegians have two different written languages (and the average Norwegian might not even speak any of those, as there are many dialects in Norway). One of those written languages is based on Danish from when Denmark ruled Norway.

In practice Norwegians and Swedes understand each other well when speaking, as their pronunciation are similar. Similarly Norwegians and Danes understand each other in writing, as the written language (and the vocabulary) are similar.

I know a lot of Danes who do not understand Swedish or Norwegian, and those movies or TV shows are normally subtitled in Denmark.

Source: I am Danish having worked a lot with both Swedes and Norwegians.

[godelski]

Thanks, it is good to hear from a first hand source.

I guess I should also add an important note: "mutually intelligible" is a spectrum, not a binary thing. If "mutually intelligible" meant "people understand one another with no issues" then 1) they'd be speaking the same language, 2) the premise of asymmetry mentioned in my original comment wouldn't be possible in the first place.

From what I'm aware, the Nordic mutual intelligibility still requires some training and exposure (it seems you're verifying this). Much like how a person from the West Coast of the US might think someone with a heavy southern accent or heavy New York accent is unintelligible until they get some exposure (but these are still the same language!).