Gray is another excellent character for fanfiction. His cool - headedness (most of the time) contrasts with Natsu's impulsiveness. You can write about his past, his training with Ur, and how he uses his ice - make magic in creative ways. His relationship with Juvia also offers a lot of room for emotional and comical storylines within the context of Team Natsu fanfiction.
Lucy is also a good character to focus on. She has a complex backstory with her family and the celestial spirits. You can explore her growth as a mage, how she becomes stronger in controlling her spirits and her relationships within the team. For example, her friendship with Natsu and how they support each other in battles. Plus, the whole aspect of the celestial spirit world is full of potential for interesting plotlines.
Natsu is always a great choice. His fiery personality and powerful dragon - slayer magic can create a lot of action - packed scenes. He's also very impulsive, which can lead to some interesting situations at the camp, like accidentally starting a small fire during a training exercise.
Gray would be a great character to pair with them. Gray has a long - standing relationship with Natsu, and his ice magic contrasts well with both Natsu's fire and Juvia's water. Their interactions can add a lot of humor and depth to the story, like Gray constantly arguing with Natsu while also trying to work together with Juvia.
Erza is frequently paired with Natsu in these fanfictions. Given her strong and leadership - like qualities, she can take charge in agent - related situations, and Natsu can be the more impulsive force. Their interactions can range from Erza scolding Natsu for his reckless actions to them having deep conversations about their responsibilities as agents. Wendy is also a character that can be paired with Natsu. Her healing magic can be crucial during dangerous agent missions, and she looks up to Natsu, which can create a sweet and protective relationship in the fanfiction.
Erza is an interesting character to focus on in a Fairy Tail Christmas OVA fanfiction. She could enforce strict Christmas traditions at the guild, like making sure everyone has a proper gift for the gift - exchange. And her strong leadership skills would come in handy when the guild faces any problems during the Christmas celebrations, like dealing with unruly visitors or handling a shortage of food for the Christmas feast.
Seilah is also a main character in this context. She has her own set of powers and a rather complex personality in the Fairy Tail universe, which can be further explored in fanfiction.
Obviously, Natsu is a very popular character as it's in the title. He is often the center of many fanfictions. Lucy is also quite popular as she has a close relationship with Natsu in the original series. Their dynamic often plays a big part in fanfictions.
Lucy could be a main character. She was always close to Natsu in the original Fairy Tail. So when Natsu returns as an 'ex' and meets the guild again, she would likely play a big role in how he is received and in the development of the story.
Ben Tennyson himself is a great choice. His ability to transform into different aliens offers a lot of potential for interesting interactions with the magic of Fairy Tail. For example, how would his Heatblast form interact with a fire - using mage from Fairy Tail? It could be a really cool dynamic.
Shikamaru is a great character to focus on. His high intelligence makes for interesting plotlines. He can strategize his way out of difficult situations. For instance, in a fanfiction, he could be the key to solving a mystery that involves the entire ninja world.
Gray would be one of the main characters to interact with Natsu. Their friendly rivalry is well - known in Fairy Tail. Makarov, as the guild master, would also have an important role in interacting with Natsu. He might give Natsu some important tasks or just have a grandfatherly chat with him about his return.