A rødnisse named Jentungen is trying to do enough nissestreker and nissegleder to earn the long nisse cap during the ceremony on Månetoppen this year, while in Blåfjell, a blånisse named Storm makes a vow with his friend Myrtel to be the bravest ever. However, because rødnissene have picked all the blue berries from Månetoppen this year, blånissene don't have enough berries to produce blåtimen so blånissene can safely go outside.
This eventually leads to conflict between rødnissene og blånissene about who has the right to the berries on Månetoppen, and it might be up to Jentungen and Storm to find a way to end the conflict.
- Adult Fear:
Fjellmor: "Do you think the parents of that rødnisse girl are as worried about their kid as we are for Storm?"Fjellfar: "Oh, yes. That's the cost for being so lucky to have a kid, that we always have to be scared of losing them."
- Jentungen's parents being unable to find her anywhere on the farm after they had had an arguement with her over her lack of successful nissestreker, and then discovering she's left with half of the map to head to the sea to look for Grånissen.
- Storm's parents are constantly worrying about him. Related to the above, they even discuss this:
- After learning that Storm is a rødnisse, Storm's adoptive parents at one point express concern that his biological parents might want to take him back.
- Arc Words:
- Storm and Myrtel's vow to "Share all words and thoughts" and to "Be the bravest of all" keeps playing an important part and being referenced throughout the series.
- "There's a time for everything."
- Both Sides Have a Point: Both blånissene and rødnissene have good reasons for needing the blueberries. Grånissen even talks about how it's important it is to see things from two sides. This is why Storm and Jentungen can't bring themselves to open the chest containing the blue or the red hat which reveals which nisser have the rights to Månetoppen, and try to find another way to solve things.
- Continuity Nod:
- Storm's parents sometimes sing part of some of the songs from Jul i Blåfjell.
- Lillegutt is still scared of the echo in Blåfjell after the events of Jul i Blåfjell.
- Didn't Think This Through: Nissestrekene are supposed to be harmless pranks, but several of Jentungen's nissestreker result in someone getting hurt because she didn't think things through.
- Distinguishing Mark: Jentungen has a birthmark on her neck shaped like half a heart, and according to her parents, her missing twin brother had one too and together their marks made one whole heart. Queen Fjellrose realizes where Storm came from upon being shown the mark by Jentungen, and Storm later realizes that he's Jentungen's missing twin brother upon seeing it himself later in the series.
- Fantastic Racism: While the ancient law forbidding blånisser from allowing a rødnisse to enter the mountain is no longer in effect due to the events of Jul I Blåfjell, things still aren't all that friendly between blånisser and rødnisser, although a lot of it likely comes from the main conflict being how rødnissene took all the blueberries from Månetoppen, leaving blånissene with no way of creating blåtimen (the blue hour) every day of December like they normally do, as well as meaning they can't go outside. By the end of the series, it seems they're all getting along better than before.
- Half-Human Hybrid: Jentungen believes Mamsen and Lillegutt to be some sort of half-human half-nisse hybrid due to mishearing their talk about "business" as them referring to themselves as "buis-nisser".
- Happily Adopted: Storm, who is aware he is adopted, although none of the blånissene are sure who his parents really are. What he doesn't know until later is that he was in fact born a rødnisse, and is Jentungen's twin brother.
- Maybe Magic, Maybe Mundane: In one of the last episodes, Storm offers to lend his mother the blue stone so she can go outside with him when it's not blåtimen, but she then points out that since Storm was born a rødnisse, and thus wouldn't disappear when outside when it's not blåtimen anyways, they have no way of knowing whether the blue stone really does work or not.
- My God, What Have I Done?: Both Jentungen and her mother have a moment of this in episode 19.
- Jentungen realizes how worried her parents must be because she left without telling them where she was going.
- Jentungen's mother regrets telling Jentungen not to come back inside until she had pulled off the world's biggest nissestrek while she was angry.
- Once an Episode: The song Jentungen and/or her parents sing at the beginning and end of each episode. Episode 17, which takes place mostly at night, has Jentungen's mother commenting that since that day turned out so strange, they should probably sing the good night song even though it's currently morning.
- Reasonable Authority Figure: We already knew from Jul I Blåfjell that Queen Fjellrose was this. Here we find out that it also very much applies to Kongsgårsnissen, the king of rødnisser, who's very friendly and accepting, and seems free from the prejudices that most of his people harbor.
- Separated at Birth: Jentungen had a twin brother named Guttungen, who went missing during a storm shortly after they were born. He was found by blånisser when Myrtel was born around the same time, and while they weren't sure where he had come from, they gave him the name Storm and raised him as one of their own.
- The Un-Reveal:
- Since both rødnissene and blånissene have their reasons for needing the blue berries on Månetoppen, Jentungen and Storm ultimately decide not to open the box which contains either a red or a blue hat showing which nisser have the rights to Månetoppen, and instead try to settle the differences between rødnissene and blånissene.
- With the reveal of Storm's true heritage, we never find out whether the blue stone that he found and kept with him for most of the series actually works or not, which Storm's mother points out when he offers to lend it to her in one of the last episodes.
- What the Hell, Hero?: Jentungen's mother to Jentungen in episode 18 after finding out that another one of Jentungen's nissestreker gone wrong caused the human couple living on the farm to slip on ice and hurt themselves.
- Who's on First?: In episode 20, Grånissen gets a bit confused when he hears Jentungen calling out for Storm, since the weather is just fine.