One common theme could be adventure. They might embark on some kind of journey together in the fanfiction. For example, exploring a new land or solving a mystery.
I'm not sure specifically where to find bridget x king gristle fanfiction. You could try searching on some popular fanfiction websites like Archive of Our Own (AO3). They have a large collection of various fanfictions, and you might be lucky to find some related to this pairing there.
They might get really excited and start comparing it to their own experiences in the Trolls world. Maybe they'll laugh at the funny parts or feel inspired by the creative interpretations in the fanfiction.
Well, in fantasy fiction, cave trolls differ from other trolls in several ways. For one, their physical features might be more suited to cave living. They could have a thicker hide to protect against cave - related hazards. In terms of behavior, cave trolls are usually more territorial about their caves. While other trolls might be more nomadic or have a wider range of movement. Also, the diet of a cave troll is likely to be more limited to what is available in or near the cave, such as bats or underground fungi, as opposed to other trolls that might have a more diverse diet depending on their habitat.
I'm not sure specifically who Bridget Barton is within the context of Fantastic Fiction. It could be an author, a character, or someone related to the Fantastic Fiction community. More information would be needed to give a more definite answer.
The Trolls origin story is that they come from a magical land filled with music and color. They are small, furry creatures with a love for fun and celebration. Their world was once threatened by the Bergens, who saw the Trolls as a source of happiness (which they could gain by eating them). But the Trolls managed to survive and keep their positive spirit alive through their music and unity.
In most cases, it is legal to watch Trolls fanfiction. Fanfiction is a form of creative expression by fans, and as long as it doesn't violate any copyright laws in terms of using original characters inappropriately or stealing the main plot of the official work, it's okay.