The characters can be integrated by having them face a common threat. For example, a dark force that is affecting both the Pokemon world and the Warrior territories. So, Ash from Pokemon and Firestar from Warriors could team up to fight this evil. They would have to combine their knowledge and skills to succeed.
One way to integrate them is through a magical portal. The Warriors could accidentally stumble into the Pokemon world through a portal. They would then meet Pokemon trainers and start learning about the Pokemon. Maybe some of the Warriors would befriend certain Pokemon and form teams similar to how trainers do. At the same time, Pokemon trainers could also visit the Warrior world and learn about their ways of life and fighting styles.
They can be integrated by having a shared goal. Let's say there is a powerful artifact in both worlds that is needed to maintain balance. Characters from both Pokemom and Warriors could embark on a quest to find this artifact. During this quest, they would exchange their cultures, values, and skills. For example, a Warrior could teach a Pokemon trainer how to use a bow and arrow, while the trainer could show the Warrior how to train a Pokemon to be more obedient and powerful.
In Pokemom Warriors crossovers fanfiction, you could have a situation where the Pokemon and the Warriors swap abilities. The Warriors could gain the ability to use Pokemon moves like Teleport or Fly. Meanwhile, the Pokemon could gain the physical combat skills of the Warriors. This would lead to some really interesting battles and interactions. For instance, a Bulbasaur with sword - fighting skills would be a very unique and powerful creature in this crossover world.
The characters can be integrated through a common case. For instance, a murder that has forensic evidence only Brennan's team can handle and a mystery - writing angle that Castle is interested in. They would meet at the crime scene and start collaborating.
One way to integrate them is through a common enemy. Maybe a new villain emerges that has powers related to both the Twilight and Flash universes. The vampires and werewolves from Twilight could team up with the Flash and his allies to fight this enemy. They would need to learn about each other's abilities and work together. For example, the Flash could use his speed to distract the enemy while the Twilight characters use their super - strength or mind - control powers to defeat it.
For starters, you can focus on their skills. For instance, the Stargate characters' knowledge of different cultures and advanced technology can be paired with the Sentinels' unique abilities like their enhanced senses. Daniel Jackson from Stargate could study Sentinel culture, while a Sentinel could use their senses to help Jack O'Neill in combat situations.
Another way is through shared villains. Say a villain has the ability to travel between the two universes and is causing chaos in both. This would force the heroes to come together. For instance, Loki could find a way to the Arrowverse and start causing trouble. The Arrowverse heroes would be out of their depth dealing with a god of mischief, so they call in the Avengers for help. The two groups would have to learn about each other's abilities and strategies to take on Loki.
The key is to find common ground. For example, both shows deal with the supernatural. So, a plot where a powerful supernatural entity threatens both the world of Supernatural and Mystic Falls would bring the characters together. Sam's knowledge of lore could combine with Bonnie's magic skills to fight this entity.
You can also integrate them through shared technology or concepts. For instance, the power source in the Halo universe could be related to some meta - human power in the DC universe. This could lead to a scientific exploration in the fanfiction where characters from both universes collaborate to understand and utilize this connection.
To integrate the characters well, start with their personalities. Mario is generally cheerful and brave, while Link is more stoic and determined. In a fanfiction, they could learn from each other. Link could teach Mario how to be more patient in combat, and Mario could show Link how to have more fun during their adventures. When it comes to the other characters, like Luigi and Zelda, they could have their own sub - plots. Luigi might be a bit intimidated by the more serious Hyrule environment at first, but then find his own way to contribute, just as Zelda could bring her wisdom to the Mushroom Kingdom.
The characters could be integrated through a space - time rift or some sort of experimental teleportation accident. For instance, a group of Titanfall Pilots could suddenly find themselves in the middle of the Mass Effect galaxy. They would then have to adapt to the new environment and find a way to get back home, all while getting involved in the local conflicts.
The characters can be integrated in various ways. Danny could befriend Hiccup as they both have a sense of being different from their peers. Danny is a half - ghost and Hiccup was initially seen as an outcast among the Vikings. They could share their experiences of not fitting in. Astrid could be curious about Danny's powers and train with him, learning new combat techniques that combine Viking fighting skills with Danny's ghostly moves.