What could be an interesting plot for a Mario Splatoon crossover fanfiction?

Once upon a time, Mario found himself in the world of Splatoon. He was confused at first, looking at all the inklings and octolings. But being the brave hero he is, he decided to join in the Turf War. He jumped around, using his plumber skills to dodge the ink blasts. Mario's red cap stood out in the colorful ink - covered battlefield. He soon made friends with some inklings who taught him how to use the ink guns. Together, they fought against a group of octolings and won the Turf War. It was a strange but exciting adventure for Mario.

Well, perhaps Bowser somehow makes a deal with some of the more malevolent characters in the Undertale world, like Flowey. Then Mario has to not only deal with Bowser but also the new threats from the Undertale realm. He might have to learn about the concept of LOVE and EXP in the Undertale world to fully understand how to defeat his enemies. And along the way, he could meet Sans and Papyrus, and they could have some really funny exchanges due to their very different personalities.

Maybe the Mushroom Kingdom is in trouble. A strange magical force is draining all the power - ups. Mario discovers that this force is linked to Equestria. He travels there and meets Rarity. Rarity is impressed by Mario's unique style and decides to help him. They find out that a corrupted magic crystal in Equestria is causing the problem. So they have to find a way to purify the crystal. Along the way, they face many challenges, like dealing with jealous unicorns who don't want an outsider like Mario interfering in their world.

A great plot could involve a new threat that is a combination of the dark forces from both universes. Naruto and Mario find themselves in a strange new dimension where the rules of both their worlds blend. They must learn to trust each other and combine their unique skills. For example, Mario's invincibility star could enhance Naruto's speed and strength during battles, and Naruto's sage mode could help him sense hidden traps in the Mushroom Kingdom like he does in his own world.

One possible plot could be that Mario and Kirby's worlds are somehow merged due to a powerful villain's spell. They have to team up to find the source of the spell and break it. Along the way, Mario could use his jumping and power - up skills while Kirby uses his ability to copy enemies' powers. They might encounter challenges like a new type of Goomba that can fly like some of Kirby's foes.

One possible plot could be that Mario and Luigi are exploring a new world and accidentally stumble upon the Pokemon world. They team up with Ash and Pikachu to stop Bowser who has teamed up with Team Rocket to steal all the Pokeballs and use the Pokemon's power to take over both the Mushroom Kingdom and the Pokemon world.

A plot could involve an experiment gone wrong in the One Punch Man world that creates a rift, pulling in inklings and octolings. Genos and Saitama have to deal with these new, ink - based beings. The inklings mistake Saitama for a super - strong boss - like character and try to challenge him. Saitama, of course, defeats them with one punch, but then realizes they're not really bad. So he teams up with them to stop the real threat, which is a mutated sea creature that has been affected by the same experiment and is now attacking both worlds.

Imagine that Michael Rosen is from a parallel dimension where everything is made of words. When he enters Mario's world, he starts to turn the enemies into harmless words. Bowser, seeing this as a threat, tries to stop him. Mario and Michael team up. Michael uses his word - changing ability to weaken Bowser, and Mario gives the final blow. In the end, they learn from each other and Michael returns to his word - dimension, but not before leaving behind some magical word - seeds that grow into beautiful story - trees in the Mushroom Kingdom.

One idea could be that Naruto characters are transported into the Splatoon world. They might initially be confused by the ink-based battles and the unique species. For example, Naruto could mistake an Inkling for a strange ninja from another land and challenge them to a friendly spar, only to find out about the ink shooting mechanism. Another plot could involve the Akatsuki from Naruto trying to steal the valuable ink resources in the Splatoon world for their own purposes. They would face off against the Splatoon heroes who are determined to protect their world's resources.

The fanfiction could revolve around a new character who has the ability to traverse between the Splatoon and Persona 5 worlds. This character discovers a conspiracy that if not stopped, will merge the two worlds in a disastrous way. The character enlists the help of both the Inklings and the Phantom Thieves. They have to overcome their differences in fighting styles and cultures to save both their worlds. The inklings' turf war strategies could be adapted to the battles in the Metaverse, and the Phantom Thieves' stealth could be useful in the Splatoon world.