A young and curious human with a special gift, like the ability to see spirits, would also be a good pairing. Harlequin could take the human under his wing and show them the wonders of the fairy world, while the human could offer a fresh perspective on things that the Fairy King may not have considered before.
One idea could be the Fairy King Harlequin going on a quest to find a lost magical artifact that is crucial for the survival of his fairy realm. Another could be him forming an unlikely alliance with a mortal to face a common enemy that threatens both the fairy world and the human world.
They could be described as iridescent, with a sheen that changes color depending on the angle of the light. For example, in the sunlight they might shimmer like a rainbow, adding to the Fairy King Harlequin's otherworldly appearance.
A fanfiction could revolve around the origin of the Fairy King Harlequin's wings. It could explore how he got them, whether it was through a powerful spell, a gift from another magical being, or something more mysterious. For example, perhaps his wings were a result of a self - sacrifice he made long ago, and now they hold great significance in the fairy kingdom.
Kirby and Natsu would make a great pair. Natsu's fire - based magic and Kirby's ability to absorb and copy abilities could create some really cool combat combinations. They could both be hot - headed in their own ways and charge into battles without much hesitation.
Juvia is an obvious choice. Their relationship in the original series is full of interesting dynamics. Juvia's over - the - top love for Gray can lead to many comical and heartwarming situations in fanfiction. Another good option is Natsu. Their friendly rivalry can be explored further, like having them team up against a powerful enemy they couldn't defeat alone.
Lucy would also be a good pairing. She's intelligent and has a wide range of celestial spirits at her disposal. Sora could learn a lot from her about magic, and together they could use their different skills to solve mysteries or defeat enemies. Maybe Sora has some knowledge about the celestial world that Lucy doesn't, and they can share and grow together.
Natsu could be a great character to pair with Kinana. He's adventurous and his warm personality could bring out different sides of Kinana. Also, Gray would be an interesting choice. His cool and sometimes aloof nature could contrast well with Kinana's more reserved self. And Erza, with her strong leadership and warrior spirit, could form a great partnership with Kinana in a fanfiction, perhaps teaching her some combat skills.
Natsu would also be an interesting choice. Natsu's brash and impulsive nature could contrast well with Mystogan's more reserved and calculated personality. They could start off not getting along but then grow to respect each other during a difficult quest.
For a Fairy Tail Mard Geer fanfiction, Mirajane could be an excellent character to pair with him. Mirajane has her own dark past and her demon powers which could relate to Mard Geer in some ways. Their interactions could be full of mystery and tension. Laxus is another one. Laxus' brash and powerful personality would clash with Mard Geer's, creating a story full of action and power struggles. Additionally, Cana could be paired with Mard Geer. Cana's laid - back but also cunning nature could play off well against Mard Geer's more serious and evil demeanor.
Lucy Heartfilia could be paired with Zancrow. She has a different set of abilities and a more diplomatic personality. Her interactions with the hot - tempered Zancrow could lead to some interesting character development for both. She might try to reason with him or use her celestial magic in unexpected ways against his fire attacks.