Create a character who has the ability to communicate with the bar itself. The bar could have a personality of its own, and this character can understand its needs. Maybe the bar is sad because it's not getting enough magic energy, and the character has to find a way to fix it while also dealing with the other Fairy Tail members.
You could give a character the power to manipulate the drinks in the bar. For instance, they can make a cocktail that gives temporary super strength or the ability to see through illusions. Just think of how that would interact with the other characters and the story.
You can combine the characteristics of robots and the magic from Fairy Tail. For example, a robot character could have a magic core that gives it special powers. It might be able to transform into different forms depending on the type of magic it absorbs. Another way is to give the robot a personality based on its function. If it was designed as a healer - type robot, it could be very gentle and nurturing.
You can give your Changeling character unique physical traits even when they change forms. For example, they might have a distinctive eye color that remains the same no matter what form they take.
You can start by changing their backstories. For example, if you want to make a unique Lucy, instead of being from a rich family, she could be an orphan raised by street mages. This would change her personality and how she approaches magic. She might be more street - smart and less naive.
For Earthland characters, you can draw inspiration from different cultures and mythologies on our own Earth. For example, if you want to create a mage with water - based magic, you could base their appearance and personality on the mermaids or water spirits from various folklore. In Edolas, since it has a different magic system, you could create characters whose powers are related to the technology - like magic there. Maybe a character who can manipulate the magical energy in machines.
You can give them unusual magic powers. For example, the power to control shadows in a very distinct way, like creating living shadow creatures. Also, give them a unique backstory. Maybe they were raised by a group of magical beasts instead of humans. This would make their perspective and behavior different from the regular Fairy Tail characters.
You can start by combining the traits of different Celestial Spirits. For example, take the loyalty of one spirit and the mischievousness of another to create a new and interesting character.
Create relationships for them. Gemini could have a special bond with another character in Fairy Tail, like Natsu. They could start off not getting along but as they go on adventures together, they learn to respect and rely on each other. This kind of relationship building makes the character more engaging as readers will be interested in seeing how their interactions develop.
One way is to focus on the differences in the cultures of the three. In Naruto, there is a strong sense of honor and clan loyalty. In Fairy Tail, it's more about friendship and the guild. The angel could represent a different set of values, like purity and divine justice. A plot could be built around how these different values clash or come together. For example, a character from Naruto might be initially distrustful of the Fairy Tail way of life because of their different values, but with the help of the angel, they learn to appreciate it. And then there could be a quest that is based on these combined values, like saving a world that has lost its sense of all of these things.
First, consider their magic. For a Wizard Saint, it should be something very powerful and perhaps a bit rare in the Fairy Tail world. It could be a combination of different types of magic, like a blend of fire and time magic.
To create believable characters, first, study the existing characters in Fairy Tail. Notice their traits, like Natsu's impulsiveness or Lucy's intelligence. Then, when creating new characters in the hospital setting, give them flaws. For example, a doctor character could be overly confident in their skills but make mistakes. Also, give them goals. Maybe a nurse wants to learn magic to better heal the mage patients. Their backstories should also make sense. If a character is from a poor family, they might be more motivated to work hard in the hospital for a better life.