Maybe there's a plot where an ancient artifact is discovered in the city. This artifact has a connection to White Tiger's heritage. Spider - Man and White Tiger must protect the artifact from a group of thieves who want to use its power for evil. As they guard it, they learn more about each other's pasts and grow closer as friends and allies.
A good plot could be that a strange virus is spreading in the city that affects only people with superpowers. Spider - Man and White Tiger are among the affected. They have to find a cure while dealing with the symptoms that are weakening their powers. In the process, they rely on each other more than ever and discover new aspects of their friendship.
One idea could be Spider - Man teaming up with a new, original superhero created just for the fanfic. They could face a villain who has the power to manipulate time, causing chaos in New York. Another could be exploring what would happen if Spider - Man lost his powers temporarily and had to rely on his wits and the help of his friends to stop a crime wave.
One idea could be that Spider Man and White Tiger team up to fight a new super - villain in the city. Maybe this villain has the power to control minds and is causing chaos. Another plot could involve White Tiger getting kidnapped and Spider Man has to use all his skills to rescue her. He might have to face some tough obstacles along the way.
One plot idea could be that White Tiger and Spider - Man team up to fight a new supervillain in the city. Maybe this villain has the power to control technology and is causing chaos in the city's infrastructure. Another idea is that White Tiger gets accidentally caught in one of Spider - Man's webs during a fight, and they initially have a misunderstanding but then realize they can work together better. A third plot could be that there is a magical artifact that both White Tiger and Spider - Man are after, for different reasons, and they have to figure out how to share or protect it.
Another plot idea is that the OC is a scientist who accidentally creates a new type of symbiote. This symbiote has different properties compared to Venom and Carnage. Spider - Man has to team up with the OC to control and understand this new creation, leading to a lot of action and character development.
In an 'ultimate spider man crossover fanfic', a really interesting crossover could be with Venom. But instead of being enemies, they team up. Maybe there's a new symbiote - like threat that is even more powerful and they have to combine their powers to defeat it. Another idea is a crossover with the Guardians of the Galaxy. Spider - Man gets accidentally transported into space and has to team up with Star - Lord and the gang to get back home while also fighting off some space - pirates.
A possible storyline is that there's a misunderstanding between them at first. Maybe Spider - Man suspects White Tiger of being involved in something shady, but later they find out it was all a set - up by an enemy. This would lead to a great character - development arc for both of them as they learn to trust each other more.
One interesting plot idea could be Spider - Man teaming up with unexpected heroes from other universes. For example, he might work with a magical hero to fight a villain who has the ability to manipulate time. This would create a really cool dynamic as they combine their different skills and powers.
One idea could be creating an OC with a unique power set related to sound, like being able to manipulate sound waves for various effects such as creating sonic blasts or using echolocation. Another could be an OC who is a foreign exchange student from a technologically advanced country and brings in new gadgets to help Spider - Man. Maybe an OC who has a power to heal others but at a cost to their own health.
One idea could be that Spider Girl has to face a new villain who has the power to manipulate time. This would put her in situations where she has to correct the changes made to the timeline. Another could be a story where she teams up with other superheroes from different dimensions to fight a common threat that endangers all of the multiverse.
One idea could be a gender - bended Spider - Man facing different social expectations. For example, in the regular story, Peter Parker has his own set of challenges as a male superhero, but a female version might have to deal with things like being underestimated in a male - dominated superhero world. She could also have different relationships with the other characters. Maybe her friendship with Harry Osborn or her interactions with Aunt May would be more nuanced due to her being female.