Natsu is often a popular character. His fiery nature and strong loyalty make him a great candidate for love - centered stories. The 'blood' part could be related to his dragon - slayer heritage, which might play a role in some kind of blood - magic or a connection to an ancient dragon bloodline that ties into a love story.
Gray is also frequently used. His cool - headedness and his ice - make magic can be combined with a story about a love interest. Maybe there's a plot where his family's blood has a special power that only the one he loves can unlock, leading to an interesting blood and love - related adventure within the Fairy Tail universe.
Natsu could be one of the main characters. Given his love for food, he might be really interested in an eclair in a fanfiction. He could be on a quest to find the most delicious eclair in the Fairy Tail world. Another could be Lucy. She might use her celestial magic to help in a story related to an eclair, like finding a magical eclair that has been hidden by a celestial spirit.
Natsu is often involved. His powerful fire magic could be a key factor in either trying to stop the destruction or, in some cases, accidentally causing more chaos if his power goes out of control. Gray, with his ice magic, might be there to counterbalance Natsu's heat or work together with him to face the threats.
Definitely Natsu. He's always getting into trouble with his brash actions, so he's a prime candidate in punishment scenarios. Then there's Lucy. She's new to the guild in a way and still learning the ropes, so she could easily find herself on the receiving end of a punishment. And of course, Makarov, as the guild master, is often involved in doling out or dealing with punishments for the members of Fairy Tail.
Lucy is also a common character. Her celestial spirit magic gives a lot of room for creativity. Fanfiction might show her summoning spirits in new and unexpected ways or forming deeper bonds with them.
Edward and Bella from 'Twilight' are often used in difficult love fanfiction. Their relationship has elements of danger and the struggle between Edward's vampire nature and Bella's human existence. Another pair could be Harry Potter and Hermione Granger. Some fanfictions explore a more romantic relationship between them, which is difficult considering their strong friendship and the overall plot of the original series.
Natsu and Gray are often popular choices. Their contrasting personalities and magic types make for an exciting swap. Natsu's fiery and impulsive nature combined with Gray's ice - make magic or vice versa can lead to some really interesting stories.
Another pair that can be used as twins are Erza and Mirajane. Erza, the strong and disciplined knight - like mage, and Mirajane, the sweet and sometimes mischievous barmaid with powerful transformation magic. In fanfiction, if they were twins, their upbringing and how they developed their magic could be explored. There could be a story about how they support each other through tough times in the guild, and how their different personalities complement each other in battles and in their relationships with other guild members.
Xena herself is obviously a central character. Gabrielle is also often involved, either as a confidante to Xena in her accidental love situation or sometimes even as a potential source of romantic tension if the story takes an interesting turn.
Gray might also be involved. Since he has his own rivalries within the guild, in some fanfiction, these rivalries could cross the line into bullying - like behavior from either side. And then there's Lucy. As a new member initially, she could be on the receiving end of bullying from those who are more established in the guild in certain fan - created stories.
One popular mermaid character could be Lisanna. Although she's not originally a mermaid, in some fanfictions, she might be transformed into one. Her kind and gentle nature would make her a very likable mermaid character in love stories. Another could be Lucy. If she were to be a mermaid in fanfiction, her strong - willed and adventurous spirit would add an exciting dynamic to the love story. She could be in love with a character like Natsu, and their relationship would be full of fun and challenges.