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.
One interesting plot could be that Bowser teams up with the Octarians in the Splatoon world. He wants to use their ink technology to take over both the Mushroom Kingdom and the Splatoon world. Mario has to then form an alliance with the inklings. He travels through different ink - filled levels, learning new skills like swimming in ink and using ink - based weapons. Along the way, he discovers secrets about the connection between the two worlds. They finally face Bowser and the Octarian leader in a huge battle where Mario combines his classic moves with the ink - powered attacks of the inklings to save both worlds.
Once upon a time, Mario found himself in the magical world of MLP. He was quite confused at first, with all the colorful ponies and floating castles. But being the brave hero he is, he decided to explore. He met Twilight Sparkle, who was intrigued by this strange new being. Mario showed her his jumping skills, and Twilight was amazed. They then went on an adventure together to find a way to send Mario back to his world, facing all kinds of challenges along the way, from evil magic spells to tricky terrains.
A crossover with Pokémon could also work well. The inklings and octolings could enter the Pokémon world and start trading Pokémon while also using their ink skills in Pokémon battles. For example, they could use their ink to create obstacles or distractions during a Pokémon battle, adding a new and interesting dynamic to the battles.
The combination of different universes is the most interesting part. For example, when Splatoon 2 characters cross over with Pokémon, seeing the inklings and octolings interact with Pokémon and use their ink powers in the Pokémon world is really cool.
Another theme is friendship. When Mario meets characters from different franchises, they often have to work together. In a Mario and Zelda crossover, Mario and Link may start off as strangers but quickly become allies through their shared goal of defeating the evil force. They learn about each other's strengths and weaknesses and form a bond. And in a crossover with Pokémon, Mario might make friends with Pokémon trainers and Pokémon alike.
Once upon a time, Michael Rosen found himself in the Mushroom Kingdom. Mario was on a mission to rescue Princess Peach as usual. Michael, being his curious self, decided to tag along. He started telling his famous stories to Mario as they hopped over the mushroom platforms. Mario was initially confused but soon found the stories quite interesting and it gave him new energy to face the challenges ahead. Together, they defeated Bowser in a rather unconventional way. Michael used his words to outwit Bowser while Mario did the physical fighting.
Begin by creating your main characters from both universes. If it's a Splatoon and Sonic crossover, think about how the inklings would interact with Sonic and his friends. You can start with a simple situation like a race where the inklings' ink abilities give them an advantage in some parts of the track. Then build on that, adding more complex story elements as you go.
Adventure is also a big theme. The characters embark on new quests in unfamiliar settings. For instance, if Naruto is in the Mushroom Kingdom, he has to figure out how to deal with Goombas and Koopas while still maintaining his ninja skills. And for Mario in the Hidden Leaf, he has to adapt to the more dangerous and stealth - based ninja world. There's also the theme of power, as they combine their unique powers to face challenges.
To start a Mario and real - life crossover fanfiction, consider the 'why'. Why is Mario coming to our world? Is it to save it from a new threat that has somehow crossed over from his world? Or is it simply an accident? You could start with a dream sequence where a character in the real world dreams of Mario, and then wakes up to find him actually there. This allows for an interesting start as the character has to quickly come to terms with the fact that their dream has become a reality.