Reptile's ability to blend into his surroundings could be used for stealth missions in the story. For example, he could spy on an enemy and pass the information to Mileena. Mileena, with her sai skills and enhanced speed, could then lead an attack based on that intel.
Perhaps a story where a magical spell goes wrong and their minds are swapped. They have to live in each other's shoes. Reptile experiences Mileena's struggle with her Tarkatan side and Mileena understands Reptile's loyalty to Shao Kahn in a new way. Through this, they gain a deeper respect for one another.
Mimikyu has the ability to create illusions. In the fanfic, it could use this ability to protect Pikachu. For example, when a powerful and dangerous Pokemon attacks them, Mimikyu could create an illusion of a much stronger Pokemon to scare it away. Pikachu's electric abilities could be used to power up Mimikyu's illusions, making them more realistic. They could also use their combined skills to solve puzzles. Say there's a maze that is protected by electric barriers. Pikachu could discharge electricity to temporarily disable the barriers while Mimikyu creates an illusion of the correct path for them to follow.
Their different cultures can be shown through their clothing. For example, Mulan's traditional Chinese dress and Shan Yu's more nomadic, rough - hewn clothing. When they interact, they can comment on each other's attire. Also, food can be a part of it. Mulan could introduce Shan Yu to Chinese cuisine like dumplings, and he could share his people's dried meats and fermented milk products.
Neeko can shape - shift and Nidalee has her spear - throwing and hunting skills. In a story, Neeko could shift into a small animal to scout out an area, and then relay the information to Nidalee. Nidalee could then use her accurate spear - throwing to take out threats that Neeko has identified.
Slenderman's ability to be invisible or blend into the shadows could be combined with Enderman's teleportation. For example, Slenderman could hide in the shadows while Enderman teleports them both quickly away from danger. Or Enderman could teleport to a location and then Slenderman could use his spooky presence to create a diversion while Enderman steals an important item.
Pitch's ability to manipulate fear and Elsa's ice powers can be integrated in a way that Elsa's ice represents purity and light, which is the opposite of Pitch's fear - based darkness. For example, when Pitch tries to attack a village, Elsa creates ice barriers that not only physically protect the village but also act as a symbol of hope that dispels the fear Pitch is spreading.
Another way is for them to use their abilities for exploration. Rayquaza can fly high and far, carrying Latias with it. Latias can then use her psychic powers to sense things that are hidden or far away. For instance, they could be looking for a lost Pokémon or a special item. Rayquaza's speed and flight range combined with Latias' sensing abilities would make them a great team for such quests.
In a story, they could also combine their abilities in a non - combat way. Naruto's ability to connect with people could be used to gather allies. Yugito's knowledge of the tailed beasts could be used to gain more information about a certain threat. Fu's water - sensing abilities could be used to find hidden locations. For example, if they are looking for a hidden lair of an enemy. Fu could sense the presence of water sources near the lair, Yugito could use her knowledge to figure out if there are any tailed - beast - related defenses, and Naruto could convince any nearby villagers to help them in their search.
Smolder is a dragon, so her strength and natural inclination towards hoarding could play a role. For instance, she might be protective of Ocellus in a way that's similar to how she guards her treasures. Her fiery nature can also add drama, like when she gets angry or passionate about something. Ocellus, being a changeling, can use her shape - shifting abilities. She could transform into different forms to help them in various situations, like becoming a small creature to access a tight space or imitating an important figure to gain an advantage. Their different species traits can create interesting conflicts and resolutions in the fanfiction.
For Spongebob, his ability to absorb water could be a unique trait in the human world. Maybe he accidentally soaks up a spilled drink in a restaurant and causes a big mess. As for Sandy, her acorn - shaped house could be like a unique little haven in the human neighborhood. People might be curious about it.