As you write, make sure to balance the characters from both universes. Give each character their moment to shine. For example, if it's a crossover with 'Power Rangers', let the Rangers use their powers to help Martin in a big battle, but also let Martin use his knowledge of the supernatural to figure out the true nature of the enemy. Also, keep the writing style of Martin Mystery in mind, with a bit of humor, action, and mystery throughout the story.
First, you need to decide which other universe you want to cross it with. Once you've chosen, study both the Martin Mystery world and the other world's lore, characters, and settings. For example, if it's with 'Ben 10', understand how the Omnitrix works and the types of aliens Ben can transform into, as well as Martin's gadgets and how his team operates.
Start by researching both Martin Mystery and the other property you want to cross it with. Know the characters, their personalities, and the rules of their respective universes. Then, come up with a central mystery or problem that can only be solved by the combined efforts of the characters from both. This will give your fanfic a strong focus and keep the readers interested.
One idea could be to cross Martin Mystery with another supernatural - themed show like 'Scooby - Doo'. Martin and the gang could team up with Scooby and the Mystery Inc. to solve a mystery that involves both their universes. Maybe it's a mystery where the monsters from Martin's world are being controlled by a villain from Scooby's world.
To start writing a chara crossover fanfiction, you should start with brainstorming ideas for how the characters will interact. Will they be friends or foes at first? Also, think about how the different rules and worlds of the original characters will blend or clash. For example, if you're crossing a magical character with a non - magical one, how will that work? Sketch out a rough outline of the story, including the beginning, middle, and end. You can start with a simple premise like 'What if these two characters met?' and then build on it. Consider the character arcs for each of the crossed - over characters. How will they change during the story?
Begin by brainstorming ideas. Think about what would happen if the 'legion' met a different group of characters. You can draw inspiration from other crossover fanfictions you've read or movies/TV shows you've seen. After that, develop your characters. If you're bringing in characters from different universes, give them new dynamics. They might be initially suspicious of each other but then learn to work together. And don't forget to set the scene. Describe the new world that is created by this crossover, whether it's a mix of the 'legion' world and another or a completely new place where they all end up.
To start writing 'Battletech Crossover Fanfiction', begin by choosing a crossover that has potential for great stories. Say you pick 'Battletech' and 'Full Metal Panic'. Research both universes thoroughly. Next, create a strong plot. Maybe the mechs are being used in a war on a planet similar to the one in 'Full Metal Panic'. Develop your characters well, like how a Battletech pilot would react to the situations in the other universe.
Begin by exploring the personalities of Robin and the character he is crossing over with. If it's, say, Robin and Supergirl, understand how Robin's detective skills and combat training would interact with Supergirl's superpowers. You can start with a small encounter between them, like they meet by accident and then gradually build up to a bigger adventure. Also, don't forget to add some conflict, whether it's internal (Robin struggling with his own insecurities) or external (facing a powerful enemy).
Begin by creating a character profile for Android 21 in this new crossover setting. Consider her goals and how they might change. Also, establish the rules of the new world she's in. If it's a world of magic, how will her powers interact with magic? You can start with a simple scene, like her arrival in the new world, and build from there.
I'd recommend 'Lydia's Hidden Powers'. This fanfiction delves deep into Lydia's potential powers that were perhaps not fully explored in the original. It has a lot of action and character development. You'll find yourself hooked from the very first chapter as it builds up the mystery around Lydia's newfound abilities.
One idea could be to cross Martin Mystery with another mystery - solving show like Scooby - Doo. Picture Martin and his team joining forces with the Mystery Inc. gang to solve a supernatural mystery that spans across both their universes.
In this fanfic, the setting could be a mysterious island. The Totally Spies are sent to investigate some strange energy readings. Meanwhile, Martin Mystery and his team are there looking into rumors of a cursed treasure. When they meet, there's some initial tension. However, as they start exploring the island further, they find that the strange energy is related to the cursed treasure. The Totally Spies' ability to hack into security systems and their combat training comes in handy, while Martin Mystery's ability to decipher ancient inscriptions and deal with the supernatural helps them understand the true nature of the curse. Together, they face off against a group of pirates who also want the treasure and the evil spirit that guards it.