A very frequent theme is redemption. Peter, especially, has a lot of past wrongs to make up for, and in many fanfictions, his journey towards redemption while interacting with Stiles and Derek is explored. There's also the theme of family. They form an unusual family unit, and how they adapt to that is often a part of the story.
One common theme is self - discovery. Since Derek is a complex character, many fanfictions focus on him learning more about himself. Another theme is friendship. Writers often explore the relationships he has with other characters in the story. Also, adventure is a popular theme. Derek is often put into exciting and dangerous situations in fanfiction.
Common themes would include the power dynamics between Derek and Stiles. Since Derek is in heat, there might be a shift in the power balance in their relationship. There could also be a theme of protection. Stiles might feel the need to protect Derek from potential threats while he's in this state. And of course, love and attraction are likely themes, as the situation could intensify their feelings for each other.
One common theme is friendship. Since they are often in the same story, their interactions and the growth of their friendship are frequently explored. Another is the supernatural aspect as they are often part of a supernatural world in these fictions.
The theme of self - discovery is also present. Through their relationship, both Stiles and Derek may discover new aspects of themselves, like their capacity for love and vulnerability.
One common theme could be action - packed moments. Stiles jumping on Derek might be part of a fight scene or a sudden, impulsive move during a dangerous situation in the story.
One common theme is the exploration of their hidden desires. Since in the original they might not have had an overtly romantic relationship, fanfiction often delves into what they might be secretly wanting from each other.
A less obvious but still present theme is self - discovery. Both characters are often on a journey of understanding themselves better. In the context of their relationship in fanfiction, this self - discovery can be influenced by their interactions with each other. For example, Peter might learn more about his capacity for good through his friendship with Stiles, and Stiles might discover new aspects of his own abilities or personality when dealing with Peter.
One common theme is the exploration of trust. Given Peter's past actions, Stiles often has to struggle with whether to trust him or not. Another theme is the power dynamic. Peter is usually more powerful in the supernatural sense, but Stiles has his own form of intelligence and strength, and how they balance this is often explored.
The theme of family is also prevalent. Even though they may not be related by blood, they form a family - like bond. Derek acts as a father figure, guiding and supporting Stiles. There's also the theme of loyalty. They stay loyal to each other through thick and thin in these fanfictions.
One common theme is the discovery of love. They often start off not realizing their feelings and then gradually come to terms with their deep love for each other. Another theme is the power of acceptance. Since Stiles and Derek are different in many ways, their journey towards accepting each other completely is often explored.