One common theme is the clash of cultures. For example, when Naruto crosses into a different universe like the Star Wars universe, his ninja culture and the Jedi culture can be very different. This creates interesting conflicts and also opportunities for Naruto to learn and grow.
Friendship and cooperation are often explored. When Naruto enters a world full of new characters, he has to make friends and allies. In a crossover with the One Piece world, Naruto's ability to form strong bonds with Luffy and the Straw Hat crew is a central part of the story. They all work together towards common goals, whether it's fighting a powerful enemy or exploring a mysterious island.
Power - up is also a frequent theme. In many crossovers, Naruto's skills are enhanced or combined with the powers of the new world he enters. For instance, in a crossover with the Dragon Ball universe, Naruto might gain new energy - based powers that are a blend of his chakra and the Saiyan's ki. This not only makes him more powerful but also changes the power dynamics in the story.
Power - up is a very common theme. Xander goes from being the 'normal' one in the group to having some extraordinary powers or skills. Also, friendship is often explored. His relationships with Buffy, Willow, and the others are either strengthened or tested as he becomes a bamf. In some stories, his newfound status makes his friends see him in a whole new light, which can be both positive and negative for their friendships.
One common theme is Merlin's hidden power being revealed to the knights. For example, in many fanfictions, Merlin shows his magical abilities in a big way to save the knights from a dangerous situation, like a powerful enemy attack.
The theme of family also plays a big role. Even though Hadrian may be a bamf (bad - ass mother - f*cker), he still has to deal with his family legacy, whether it's the Potter name or other family ties. This can create interesting storylines about how he honors or overcomes his family's past.
One common theme is redemption. Since Percy had his issues in the original series, many fanfictions focus on him redeeming himself in a bamf way, like standing up to powerful enemies or making up for past wrongs.
Friendship is a very common theme. Since it's about Naruto and his friends in a crossover, it often shows how their bonds are strengthened or tested in the new situations. For example, they might have to rely on each other more than ever.
One common theme is acceptance. The characters often have to come to terms with the mpreg situation which is not the norm in the wizarding world. Another theme is the strength of the 'bamf' characters. They usually show great resilience in the face of the challenges that come with mpreg, like dealing with the reactions of others.
A common theme is the clash of cultures. Naruto's ninja culture from his world is very different from the military - and magic - based culture in 'The Gate'. So, exploring how these two cultures interact is often seen. For example, Naruto might introduce the concept of chakra to the people of 'The Gate' world.
Character growth is also a major theme. In a long 'Naruto' crossover fanfiction, Naruto usually has to face new challenges in the crossed - over world. This forces him to adapt and grow in ways he didn't in his original 'Naruto' world. For instance, in a crossover with the 'Fullmetal Alchemist' world, he has to learn about alchemy and its rules, which broadens his understanding and skills.
One common theme is power. The shinju is a powerful entity, and when crossed over with Naruto, it often involves the characters either seeking its power or having to deal with the consequences of its power. For example, in many fics, Naruto might be tempted by the shinju's power to achieve his goals more quickly.
A common theme is the clash and then the fusion of different power systems. Naruto's chakra - based ninja skills and the magic from the other universe, like spells in Harry Potter or magic in Fairy Tail, often start by being at odds but then find a way to work together.