What could be an interesting plot for a Lucario and Fairy Tail crossover fanfiction?

Well, perhaps there could be a situation where an evil force in the Fairy Tail universe is creating portals to other dimensions to gather powerful allies. Deadpool accidentally stumbles through one of these portals. The Fairy Tail guild has to figure out how to deal with this strange, talkative, and unpredictable new 'ally'. Deadpool, on the other hand, is just excited to be in a new world full of magic and new things to fight. He could end up teaching some of the Fairy Tail members his unique combat moves, while also learning some magic from them in return.

A cool plot might be that a powerful dark wizard in the Fairy Tail world discovers a way to control some of Ben's aliens. Ben has to seek help from Fairy Tail mages to break the control and then they join forces. The Fairy Tail members are amazed by Ben's ability to transform and his alien powers, and they work together to stop the dark wizard's plan to take over both worlds.

A cool plot might be that a dark wizard from Fairy Tail discovers a spell that can open portals to other dimensions and accidentally pulls Inuyasha, Kagome, Shippo, etc. into their world. The Fairy Tail guild decides to help them get back home. But during this time, they realize that there are some similarities between the demons in Inuyasha's world and the dark creatures they fight in their own world. So, they team up. Inuyasha and Natsu could have a friendly rivalry over who is stronger and in the end, they combine their powers to defeat an ancient evil that was awakened by the portal - opening spell.

One possible plot could be that Goku somehow gets transported to the Fairy Tail world. He could join forces with Natsu and the gang to fight against a common enemy like Acnologia. Goku's power levels would be off the charts compared to most in Fairy Tail, but he'd be intrigued by their magic. Maybe he'd learn some magic himself or teach them some of his ki techniques.

Maybe there's a powerful dark magic that is threatening both the KHR world and the Fairy Tail world. So, the Vongola Family decides to team up with Fairy Tail. Tsuna could bond with Natsu over their determination to protect their friends and families. The two groups would combine their unique powers. Like, Reborn's assassination skills along with Erza's swordsmanship could create a really cool battle strategy against the common enemy.

One possible plot could be that the Fairy Tail guild discovers a strange energy similar to the ki in the DBZ universe. Natsu, being the curious and powerful wizard he is, decides to investigate. He then somehow gets transported to the DBZ world. There, he meets Goku, who is intrigued by Natsu's magic. Together, they have to face a new enemy that is a threat to both their worlds. This enemy could be a powerful wizard who has found a way to combine dark magic with the power of the dragon balls.

Well, perhaps in the fanfiction, Godzilla is a result of some dark magic experiment gone wrong in the Fairy Tail universe. The guilds have to deal with this giant creature that is causing destruction everywhere. Lucy might use her Celestial Spirits to try and hold Godzilla off while the others come up with a plan. Gray could use his ice - make magic to try and freeze parts of Godzilla to slow it down. And in the end, they find a way to reverse the dark magic and turn Godzilla back to normal or send it away.

One possible plot could be that Ben Tennyson, while on a trip with his family, somehow gets transported to the world of Fairy Tail. His Omnitrix malfunctions due to the different magical energies in that world. The Fairy Tail guild members are initially suspicious of him but when they see his alien forms in action against some common enemies like the Dark Guilds, they start to work together. Ben could learn about magic from the guild members and they could learn about his advanced technology.

One possible plot could be that Naruto, with his godlike powers, accidentally gets transported to the Fairy Tail world. He teams up with Natsu and the gang to fight a common enemy that threatens both their worlds. His unique ninja skills combined with Fairy Tail magic could create some epic battle scenes.

One possible plot could be that the Akatsuki from Naruto Shippuden somehow gets involved with the dark guilds in Fairy Tail. For example, they could form an alliance to steal powerful magical and ninja artifacts. Naruto and his friends, along with the Fairy Tail members, would then have to team up to stop them. They could start off being suspicious of each other, but as they face common enemies, they learn to trust and use each other's unique abilities.