A pet could have unique powers that are useful in both worlds. Let's say a pet has the power of invisibility in the Harry Potter world. In the RWBY world, this power could be used to sneak up on Grimm or avoid detection by enemies. The pet could also form bonds with characters from both universes. For example, it could befriend Ruby and also get along with Harry, and through these relationships, bring the two groups of characters closer together.
It could be really interesting. For example, in this crossover, a wizard from Harry Potter might have a pet that has some characteristics of the Grimm from RWBY. Maybe a cat with the ability to sense approaching danger like a Grimm, and it could use its magic to protect its owner. The RWBY characters could be amazed by the magical pets from the Harry Potter world, and there could be some comical moments when they try to interact with these strange and wonderful creatures.
A crossover could involve a magical pet from Harry Potter being transferred to the RWBY world. For example, a phoenix. The RWBY characters would be amazed by this magical creature. The phoenix could help them in battles against Grimm. It could also have a connection with one of the RWBY characters, like giving them the ability to rise from the ashes, literally or metaphorically, after a tough battle.
In a crossover fanfiction, the lightning wave could be a result of a magical experiment gone wrong. A Hogwarts student, perhaps Hermione, is researching ancient magic and accidentally creates a portal that sucks in Naruto. Together, they figure out that Naruto's lightning - style jutsu can be enhanced with Hermione's knowledge of magic, creating a new and more powerful lightning wave. This lightning wave could then be used to fight off dark forces from both the Naruto and Harry Potter universes, like the Death Eaters and the Akatsuki.
Often, it could be a plot device. For example, it might be the key to unlocking an ancient mystery in the RWBY world. Since the Sword of Gryffindor only appears to those worthy in the Harry Potter series, in RWBY fanfic, it could be that only a truly noble character can access it. And when they do, it causes a stir in the RWBY world as it's an unknown and extremely powerful object.
It could be about Harry having unique abilities as Ruby's pet. Maybe he can sense Grimm before they appear, helping Ruby in her battles. He might also have a special bond with Ruby that allows them to communicate in a non - verbal way.
One way could be through a crossover spell. Maybe a powerful dark wizard in the Harry Potter universe discovers a way to create a Rinnegan - like power. They might use it to gain ultimate control over magic, similar to how the Rinnegan gives great power in Naruto. This could lead to a new kind of threat that Harry and his friends have to face.
One way could be through a magical spell gone wrong. Maybe a spell that was meant to transform an object into a helper, like in Beauty and the Beast, but instead it affects a character in the Harry Potter universe in a similar way. For example, a student might be turned into a beast - like form and only the love of another can break the spell, much like in the original Beauty and the Beast story.
In the realm of RWBY fanfiction, the possibilities are endless. It's not unheard of for Harry Potter to be Ruby's pet. This could potentially lead to some hilarious scenarios. For example, Ruby might take Harry Potter (in his pet form) on her adventures in the RWBY world. He could use his magic in unexpected ways to help Ruby and her team out of tough situations, or maybe just cause some chaos in the process. The idea combines the magic and mystery of the Harry Potter series with the action - packed world of RWBY in a really novel way.
The musical style of Hamilton can be incorporated by having the characters break into song - like numbers. For instance, Harry could sing about his quest to defeat Voldemort in a rap - like style similar to how Hamilton rapped about his life and goals. The lyrics could be filled with references to spells, magical creatures, and the battle between good and evil in the wizarding world.
In fanfiction, the gun could be a magical - Muggle hybrid weapon. It could have been created by a wizard who was fascinated by Muggle technology. Harry gets hold of it, and it has unique properties. For example, it could fire spells instead of bullets, or the bullets could be enchanted to have special effects. This would blend the two worlds of magic and Muggle - ness in an exciting new way.