Well, you could start with the concept of a shared threat. Suppose there's a powerful dark force that is a threat to both the Pokemon world and the Fairy Tail universe. Characters from both sides would then have to team up. The Fairy Tail wizards could use their teleportation magic to quickly move around the Pokemon regions, while Pokemon with their unique abilities like Pikachu's electricity could be used to power up certain spells or devices in the Fairy Tail world.
One way is through character crossovers. For example, a Pokemon trainer could end up in the Fairy Tail world and use their Pokemon to help in quests. They might use a Water - type Pokemon like Squirtle to put out fires during a mission. Another way is to combine the magic systems. Maybe Fairy Tail magic could be used to enhance a Pokemon's abilities, like using Fire Dragon Slayer magic on a Charmander to make its flames even hotter.
One way could be through a magical portal. Maybe some Fairy Tail magic creates a portal that sucks Naruto and his ninja friends into the Fairy Tail world. Then they have to team up with the Fairy Tail mages to face a common enemy.
One way to combine them creatively is through a crossover story. For example, Naruto could be transported to the Fairy Tail world and his Kyuubi powers could be mistaken for some kind of powerful magic. The characters from Fairy Tail might initially be cautious or even hostile towards Naruto because of his unknown and powerful abilities. But as the story progresses, they could learn to work together and Naruto could teach them about his world and his ninja skills while also learning about magic from the Fairy Tail mages.
In a fanfiction, you could create a plot where the power of the White Dragon is needed to defeat an enemy that threatens both the Fairy Tail world and the Naruto world. For example, a powerful dark force that can manipulate both magic and chakra. Characters like Lucy from Fairy Tail could use her celestial spirit magic in conjunction with the ninja skills of Sakura from Naruto to fight this common foe.
One way to combine them creatively is through crossovers. Imagine a story where a character from Naruto with the Rinne Sharingan finds themselves in the Fairy Tail universe. They could use their unique abilities to face the magical challenges there. For example, the power of the Rinne Sharingan might interact in unexpected ways with Fairy Tail's magic. Maybe it could be used to analyze and counter some of the most powerful spells in Fairy Tail.
One way to combine them could be through a crossover device. For example, a powerful Pokemon like Mewtwo could accidentally open a portal to the Avengers' universe. Then, the Avengers might mistake the Pokemon for some kind of new alien threat. They would try to contain it, but soon realize that the Pokemon has no malicious intent. Meanwhile, the Pokemon trainer who follows Mewtwo through the portal has to team up with the Avengers to find a way back home and also deal with any villains in the Avengers' world that might try to use the Pokemon for their own gain.
The magic in Fairy Tail could be combined with Pokemon elements by having spells that are related to Pokemon types. For instance, a water - mage could use a spell to create a Pokemon - like water creature. Or a lightning - mage could summon an electric - type Pokemon - inspired bolt of energy.
Maybe the Fairy Tail wizards could accidentally get sucked into the Time Squad's time - traveling device. This would lead to them having to work together to get back to their own time and place. The Time Squad could learn some magic from the Fairy Tail characters, and the Fairy Tail characters could learn about time manipulation from the Time Squad.
One way could be through a magical portal or rift that causes the magic from both universes to mix. For example, Natsu's fire magic could be affected by the dark and mysterious magic of the Black Bird world, making his flames have new properties. Maybe they turn purple or have the ability to nullify certain types of magic from the Black Bird world.
Well, for a prom in Fairy Tail fanfiction, it could be a cross - guild event. Imagine Fairy Tail inviting other guilds like Sabertooth and Lamia Scale. Each guild could show off their unique style at the prom. The characters might have some friendly competitions during the prom, like a magic - powered dance - off. And of course, there would be lots of romantic moments. Natsu might be clueless about the whole prom thing at first but then have a great time with Lucy.
It could be Naruto himself. With his already powerful ninjutsu and the potential to gain Fairy Tail magic, he would be extremely formidable. His ability to quickly learn new skills and his large chakra reserve, combined with something like Fairy Tail's celestial magic, would make him a force to be reckoned with.