Planning an impromptu trip to Oslo in December. Any recommendations?

TIA

The Norwegian WWII resistance museum is fascinating if you're into WWII history.

It'll be cold

The folk (norwegian museum of cultural history) museum is great, gotta see the stave church.
The viking ship museum is closed for renovations still i think, but the Framm museum is interesting, have not been to the kontiki museum.
Jump in the fjord after spending time in a sauna, its exhilarating.
Vigeland park is... interesting.

Norwegian food is mostly boring but you can try whale legally.

You can buy a bus/tram pass that will get you anywhere in city. If Oslo S (central station) is your starting point, it's pretty easy to get around and figure out the city. Ive been twice (2019 and 2023).

Pretty much everyone speaks English. The people are reserved and not particularly chatty with strangers. Its not a sign of unfriendliness, just more inteoverted than other euro cultures.