Kristoff might also be a popular character in some fanfictions. He could be the one who helps Elsa and Anna on their adventures, providing his knowledge of the mountains and his loyalty. His relationship with Anna can also add an interesting dynamic to the story.
One interesting plot could be Elsa and Anna going on a magical adventure outside of Arendelle. They might discover a hidden land filled with unique creatures and have to use their sisterly bond and powers to overcome challenges there.
Besides Anna and Elsa, there are many characters that play crucial roles. Hans is an important one at the start. He seems like a charming prince but later reveals his true, not - so - nice self. The people of Arendelle are important too. They are the ones affected by Elsa's powers and their reactions also shape the story. And the guards in the castle are there to protect the kingdom and are part of the overall story world.
In some of these fanfictions, Sven could be a significant character. He might help Kristoff in his tasks related to Anna's pregnancy, like carrying supplies. Another character could be the trolls. They are known for their wisdom in the Frozen universe. So they could offer advice to Elsa and Anna about their pregnancies, such as how to deal with any magical complications or how to raise their children to be good and strong. And of course, the people of Arendelle are also important. Their reactions and support play a role in the story.
There could be a dark spirit that has been awakened by the little brother's emerging powers. This spirit is angry at being disturbed and decides to target the little brother. It causes chaos in Arendelle, blaming it all on the little brother. As the story progresses, the little brother has to find a way to either defeat or pacify this dark spirit to save his home and family.
Well, one possible plot could be that the little brother has some unique magical abilities that are different from Elsa's ice powers. Maybe he can communicate with animals in the enchanted forest and has to use this power to save the kingdom from a new threat.
Kristoff is often involved. He would be there to support Anna, and might be a bit nervous about becoming a father. Olaf could also be a popular character in such fanfictions. He'd be his usual cheery self, trying to make the pregnant Anna and Elsa happy with his funny remarks.
It becomes deeper. They become more reliant on each other for emotional support. Since they are both going through the same experience of pregnancy, they can share their fears, joys, and concerns. For example, they might talk about how their bodies are changing and how they will raise their children.
One idea could be that Elsa and Anna discover a hidden magical realm within Arendelle. They meet new magical creatures there and have to work together to solve a problem that threatens both this new realm and Arendelle. For example, a dark magic is spreading and only Elsa's ice powers combined with Anna's courage can stop it.
Kristoff is often a popular character to include. Since he's Anna's love interest, his presence can add an element of romance and also his skills as an ice - harvester can be useful in different time - travel scenarios. Olaf is another great addition. His naivete and charm can provide some comic relief in tense time - traveling situations. Also, the trolls could be included. They have a lot of knowledge about magic and the past, so they could play a crucial role in guiding Elsa and Anna during their time travels.