One common theme is the clash of different worlds. Inuyasha is set in a feudal era full of demons and magic, while Ranma has a more modern (but still very Japanese - culture - influenced) world with martial arts and strange curses. So when the two are crossed over, the difference in their worlds often leads to interesting plotlines. Another theme is the interaction between the characters. For example, Inuyasha's brash and impulsive nature vs Ranma's own quick - tempered but also comical personality can create a lot of humorous and tense situations.
Sure. One popular piece of Inuyasha - Ranma crossover fanfiction might be 'The Unexpected Encounter'. It combines the unique elements of both series in an interesting way. The story often has Ranma somehow ending up in the Feudal Era of Inuyasha. Another one could be 'Two Worlds Collide' which plays around with the characters' personalities from both shows and how they interact with each other in a new, fictional setting.
One idea could be that Ranma accidentally stumbles into the world of Sailor Moon. Maybe he gets caught up in a fight against a youma and the Sailor Scouts mistake him for an enemy at first. But then they realize he has his own unique fighting skills and they team up to defeat the common foe.
The setting is a common element too. When Ranma crosses over into a different world, the new setting affects his actions and the overall story. For example, if he crosses over into a post - apocalyptic world, he has to use his martial arts in new ways to survive. And of course, the humor that is characteristic of Ranma 1/2 often gets transferred and combined with the humor (if any) of the crossed - over universe.
A third idea is that there's a mix - up with the curses in both worlds. Ranma's curse of changing into a girl when splashed with cold water gets combined with some of the magic in Highschool DxD. This creates a whole new set of problems and adventures for him as he tries to figure out how to deal with this strange new situation while also trying to keep his identity a secret from the new characters he meets.
One idea could be that Sephiroth somehow gets transported to the feudal era of Inuyasha. He might initially be seen as a great threat due to his power. But as the story progresses, he could form an unlikely alliance with Inuyasha and his group against a common enemy, like a powerful demon that is even more menacing than any they've faced before.
There might be. However, the availability can depend on how popular this particular crossover concept is among fanfiction writers. Some of these crossovers might be quite rare, but if you explore different fanfiction communities and groups dedicated to either Ranma or Pokegirls, you might be able to find some recommendations or even direct links to such fanfictions.
One common theme is the interaction between the unique characters from Ranma and the world of Pokegirls. For example, how Ranma's martial arts skills might be used in the Pokegirls' universe. Another could be the exploration of different genders, as in Ranma's curse, in the context of Pokegirls.
How about a Ranma crossover with Harry Potter? Ranma could be a foreign exchange student at Hogwarts. His martial arts could be a form of magic in the wizarding world. Or a crossover with Fullmetal Alchemist. Ranma might get involved in the search for the Philosopher's Stone or help the Elric brothers with their alchemical problems. There are so many possibilities for Ranma crossover fanfiction.
Adventure is also a common theme. Picture Ranma traveling through the Pokemon regions, facing different Gym Leaders and trainers. He would bring his martial arts expertise into the Pokemon battles, which would be a new and exciting take on the typical Pokemon adventure.