One idea could be that the main characters from both games, Cole from Infamous and Alex from Prototype, team up to fight a common enemy that threatens both their worlds. Maybe a powerful virus that is mutating people in the Infamous universe and also causing chaos in the Prototype world.
Another interesting concept is a world where the powers from Infamous and Prototype are combined. For example, Cole's electrical powers could be combined with Alex's shape - shifting abilities. This could lead to some really cool fight scenes and new ways to explore the merged universes. The story could follow a new character who discovers these combined powers and has to learn how to control them while facing various challenges.
Maybe a crossover with a character from a post - apocalyptic game like Fallout. Cole could find himself in the wastelands, having to adapt his powers to the new environment and deal with raiders and mutants. He might also have to figure out how to recharge his powers in a world without modern infrastructure.
One idea could be to cross RWBY characters with characters from another popular anime, like Naruto. Imagine Ruby with the ability to use Naruto's shadow clone jutsu. Another could be a crossover with the Harry Potter universe, where the RWBY characters attend Hogwarts and have to deal with magic and dark wizards. Or perhaps a crossover with the DC universe, with RWBY characters teaming up with the Justice League to save Remnant from a greater threat.
One idea could be that the protagonist from Infamous somehow gets transported to the world of Red Dead Redemption. Maybe they have to adapt to the old - west setting and deal with outlaws while also trying to find a way back home. Their electrical powers would be a huge shock to the cowboys and bandits.
In a Prototype - Mass Effect crossover fanfiction, a possible scenario is that the Reapers from Mass Effect encounter Mercer. Since Mercer can consume and assimilate other beings, it would be interesting to see how he'd fare against the Reapers. He might be able to absorb some of their technology or even gain new powers from them. And the way the different races in Mass Effect, like the Turians or Asari, would react to his presence would also be a great plot point.
Another concept could be that a character from Lord of the Rings, like Legolas, somehow gets transported to the world of Prototype. There, he would have to adapt to the modern - day setting and deal with the infected. He could use his archery skills and elven agility in a completely different environment. His presence might also cause a stir among the military and scientific communities in the Prototype world, as they try to figure out who he is and where he came from.
A great concept could be a story where the Prototype technology is somehow introduced into the Mass Effect universe. For example, some Cerberus scientists could get their hands on Prototype samples and start experimenting. This could lead to the creation of new, dangerous hybrids that the main characters have to deal with. Or perhaps Shepard has to team up with a character similar to Mercer to fight a common enemy that is exploiting both Prototype and Mass Effect technologies.
One interesting aspect could be the unique character combinations. For example, seeing Naruto interact with characters from other universes in unexpected ways. It might also introduce new plotlines that deviate from the original Naruto storyline, like a Naruto - Harry Potter crossover where Naruto has to deal with magic in Hogwarts. Another aspect is the creativity of the fans in melding different fictional worlds together, which can lead to really cool and thought - provoking scenarios.
First, study the lore of both games. Know the rules of how powers work, the social structures in each world, etc. Then, find a common ground. Maybe it's a shared threat like a powerful, otherworldly entity that is attracted to the unique energy signatures of the powers in both universes. Make sure the characters' actions are in line with their personalities. For example, Cole is often driven by a sense of justice, so he would likely approach a situation differently than Alex, who has more of a survival - of - the - fittest mentality.
One interesting concept could be the clash of different cultures from the wild west and the 'Infamous' universe. For example, how the moral codes of the wild west, like justice served by gunslingers, might interact with the super - power - based justice in 'Infamous'.
Maybe a story where the Grimm from RWBY are infected by the virus from Prototype. This would make them even more dangerous and unpredictable. The RWBY characters would then have to figure out a way to stop the spread of this new, enhanced threat, and they might have to team up with some Prototype characters who understand the virus better.