A frequent theme is self - discovery. As Astrid experiences jealousy towards Heather, she often has to look inward and figure out why she's feeling this way. It could be that she discovers new aspects of her own personality or desires. For example, she might realize that she's been too focused on competing and not enough on her own growth. Also, themes of forgiveness and acceptance can play a role. If Astrid realizes her jealousy is unfounded, she has to learn to forgive herself and accept Heather for who she is.
There are quite a few. You can try searching on fanfiction websites like Archive of Our Own. Just type in the keywords 'Astrid jealous of Heather' and you'll likely find some interesting reads.
Another theme might be adventure. Since they are likely from a story with some sort of action or adventure setting, their relationship could be explored within the context of facing challenges together. For example, they might have to work together to save their world or community, and during that process, their bond grows. Also, themes of self - discovery could be present. As they interact with each other, they learn more about themselves and their own capabilities.
Astrid might also be jealous in a fanfic when she feels left out. Maybe her friends start spending more time with a new character and she starts to feel jealous of the new friendships forming. This can lead to her trying to win back their attention, creating a lot of drama and interesting storylines in the fanfic.
Love - hate relationships are also common. They have a very complex dynamic which can be both antagonistic and affectionate at the same time. Fanfics play around with this a lot, showing the push - and - pull between them, and how they gradually move towards a more stable and positive relationship.
One common theme is friendship. Astrid often forms strong bonds with other trainers or Pokemon. Another is exploration, as she usually goes on adventures to new places. Growth is also a theme, as she learns and becomes a better trainer over time.
One common theme could be misunderstandings. For example, Astrid might misinterpret a situation and end up doing something embarrassing as a result. Another theme could be public blunders, like tripping or saying something inappropriate in front of a large group.
One common theme could be friendship. The use of a nickname might signify a closer bond between Astrid and other characters. For example, if the nickname is something cute, it could show how friends in the story cherish Astrid.
Another theme is friendship and its evolution into something more. Many 'hiccup x heather fanfic' stories start with them as friends or allies and then gradually develop their relationship into a romantic one. It shows how their mutual respect and shared experiences bring them closer. For example, they might start by working together to defeat a common enemy and then realize their feelings for each other as they spend more time together.
One frequent theme is betrayal. Given their somewhat devious natures in their original context, fanfics might explore scenarios where one betrays the other for personal gain. Also, redemption can be a theme, where they try to overcome their past wrongdoings in relation to each other. There is also the theme of competition, as they both strive to be the best in whatever situation the fanfic presents.
One common theme is redemption. Many fanfics try to show Heather as a character who can change for the better. Another theme is friendship. They explore how Heather's relationships with other characters, especially the Plastics, can evolve. Power dynamics is also a theme, as in the original Mean Girls, Heather had a certain level of power in the school hierarchy.