In a Ben 10 and Rosario Vampire crossover fanfiction, there could be a plot where the technology of the Omnitrix gets combined with the magic in the Rosario Vampire world. Maybe Ben discovers a way to use alien powers to enhance the vampires' abilities or vice versa. There could also be a cultural clash aspect where Ben's human - alien experiences are very different from the human - vampire relationships in the Rosario Vampire world. This could lead to some interesting character development for both Ben and the Rosario Vampire characters as they learn from each other.
Well, a cool storyline might be that the villains from the Ben 10 universe somehow find their way to the Rosario Vampire world. And they start causing trouble by trying to take over the school or capture the vampires for their own evil purposes. Ben then has to team up with Tsukune and the other students to stop them. Or perhaps there could be a story where Ben accidentally gets turned into a vampire - like creature because of some magic in the Rosario Vampire world, and he has to figure out how to reverse it while still using his alien powers.
It's likely that Ben with the Omnitrix would be one of the most powerful. He has access to a wide variety of alien forms, each with their own unique abilities. For example, Heatblast could deal with cold - based threats in the Rosario Vampire world, and XLR8 could outrun any fast - moving vampires or enemies. However, some of the powerful vampires like Alucard in Rosario Vampire also have incredible strength, speed, and magical abilities. So it could be a close call between Ben in his most powerful alien forms and the top - tier vampires.
A great storyline might involve a fusion of the two worlds' mechanics. For example, the Velvet Room from Persona could have some connection to Joker's world. The Igor-like figure could offer Joker and his friends some new kind of power or knowledge that they use to combat a common foe. Or perhaps the Persona characters learn about Joker's Metaverse Navigator and try to replicate it in their world, which leads to all sorts of unforeseen consequences and adventures.
A really interesting plot could be that Santana was a vampire all along but hid it from Rachel. Then, when Rachel discovers the truth, she has to decide whether she can still love Santana. There could be a lot of internal conflict within Rachel as she grapples with her feelings for Santana and her fear of the vampire world. Also, the vampire lore in the fanfiction could bring in elements like Santana having to drink blood in a way that doesn't terrify Rachel completely.
Another could be a time - travel scenario where Naruto goes back in time and meets Rikudou Sennin. They then team up to prevent a great evil from ever arising in the first place. This would allow for a lot of character development and exploration of the Naruto universe's history.
One of the most interesting storylines could be the interaction between the different species in Mass Effect and those from Stargate. For example, how would the Asari react to the Goa'uld? The Asari are a long - lived, biotic - using species in Mass Effect, while the Goa'uld are parasitic snake - like beings in Stargate. Another cool idea is the technology exchange. The Mass Effect universe has advanced biotic and cybernetic technology, and Stargate has its own unique wormhole - based travel and Ancient technology. A fanfiction could explore how these technologies might be combined or used against each other. Also, the cultural clashes would be fascinating. The different races in Mass Effect have their own moral and ethical codes, and the same goes for the races in Stargate. How would they deal with each other's values?
One interesting storyline could be Naruto using the Sharingan to enhance his combat skills in a new and unexpected way. For example, he might combine his Rasengan with Sharingan - powered genjutsu to create a more powerful and deceptive attack.
A crossover involving a shared enemy. Maybe a new alien race that is a threat to both universes emerges. The combined forces of Babylon 5 and Star Trek would have to pool their resources. The Starfleet officers could share their scientific knowledge to analyze the new threat, while the Babylon 5 personnel could offer their street - smart combat and negotiation skills developed from their own experiences in the often - tumultuous Babylon 5 station.
A really cool storyline might involve a powerful object or spell that links the two shows. For instance, a magical artifact in 'Supernatural' that can also affect the Wesen in 'Grimm'. The characters from both shows would have to race against time to find and control this object before it falls into the wrong hands. It would be a high - stakes adventure that combines the best elements of both shows, like the family - centered themes in 'Supernatural' and the unique fairy - tale inspired world of 'Grimm'.
Well, perhaps a story where the two characters cross paths due to a serial killer case. The killer seems to be targeting people involved in the legal system, and Perry Mason is representing some of the potential victims or suspects. Ironside gets involved as the detective on the case. Their different approaches at first clash but then they start to respect each other and combine their efforts to catch the killer. They might also discover a hidden conspiracy behind the killings.
A crossover fanfiction could also explore a personal connection. What if a member of the Reagan family was a big fan of Castle's books? And then they end up meeting in a situation where they need to work together on a case. This would add an interesting layer of fan - meets - idol dynamic to the story while also dealing with the crime - solving aspect.