One exciting plot twist could be the discovery of a hidden connection between Smallville's Clark Kent and The Flash's Barry Allen that predates their superhero identities. Maybe they are related in some way through their alien or metahuman genetics. Another could be a villain who has the ability to manipulate time and space, causing chaos in both Smallville and Central City. This would force Clark and Barry to work together in ways they haven't before. A third plot twist might be that a character from Smallville who was thought to be normal actually has latent superpowers that are activated during the crossover, adding an unexpected element to the story.
Well, a really cool plot twist could be that the kryptonite in Smallville has an unexpected effect on the metahumans in The Flash's world. For example, it could either enhance or suppress their powers in strange ways. Also, what if there's a device in Central City that can reverse the effects of the yellow sun on Clark? That would be a huge twist. And then there's the idea that a long - lost relative of Barry's shows up in Smallville and has some kind of knowledge or power that is crucial for saving both worlds from a common threat.
Well, perhaps there could be a crossover where a villain from The Flash, say Reverse - Flash, teams up with a Hydra agent from Agents of Shield. This alliance would be a huge shock as they combine their powers and knowledge. Reverse - Flash's speed and ability to manipulate time along with Hydra's devious plans could create a very difficult situation for the heroes from both universes to handle.
Maybe in the fanfic, there's a villain who can absorb their powers. So when Supergirl and Flash first encounter this villain, they start losing their powers bit by bit. This forces them to rely on their wits and non - superhuman skills to outsmart the villain and find a way to regain their powers before it's too late.
A common plot twist is when a villain from one show teams up with a villain from the other. In some fanfics, like 'The Dark Alliance', Lex Luthor and a demon from Charmed join forces. This creates a really tough situation for the heroes. It's unexpected because the two shows have very different types of villains originally.
Perhaps in the fanfiction, there's a time - traveling aspect. Barry's time - traveling experiments go wrong and he ends up in Smallville during Clark's high school years. They have to figure out how to get Barry back to his own time while also dealing with a villain who is trying to change the future by targeting Clark in the past. This could involve both of them learning about each other's powers and how to work together effectively.
The Reverse Flash could also be a main villain in this crossover. He travels to the Smallville universe to cause trouble. He might target Clark, thinking that by eliminating him early, he can change the future in his favor. This would force Barry and Clark to work together to stop the Reverse Flash's evil plans.
A plot twist could be that a character from one of the shows, who seems to be a minor or unassuming figure, is actually a powerful being from the future sent to manipulate the events of the crossover. This person has been subtly guiding the actions of the heroes, and when the truth is revealed, it completely changes the heroes' perception of the events they've been through and who they can trust.
Well, perhaps there could be a situation where the Force in the Star Wars world interacts with The Flash's speed force. For example, some Sith Lords could try to harness the speed force for their own dark purposes, and The Flash has to team up with the rebels to stop them. He could also teach some of the Jedi his unique way of moving super fast, which could give them an edge in combat.
Clark and Barry would likely start off as cautious allies. Clark, being more experienced in the superhero game in a sense, might initially be a bit of a mentor to Barry. But as they face challenges together, they'd become true friends. Lois Lane would probably be intrigued by Barry's speed and his different approach to reporting. She might even try to get some scoops from him. Meanwhile, Chloe Sullivan could help Cisco Ramon with some of his tech issues, and they'd form a bond over their shared love of all things tech - savvy.
One exciting plot twist could be Spider - Man's web - slinging abilities affecting the Grimm in RWBY. Maybe his webs are able to hold the Grimm in a way that the Huntsmen and Huntresses in RWBY have never seen before. This could change the way battles are fought. Another could be that Spider - Man has to adapt to the world of Remnant, where the rules of physics and combat are different from his own world. For example, he has to figure out how to deal with Dust, the energy source in RWBY, and incorporate it into his fighting style.
One exciting plot twist could be Ben using his alien forms in unexpected ways within the Attack on Titan world. For example, using Heatblast to melt through the Titans' hard exteriors in a crucial battle. Another could be a character from Attack on Titan getting the Omnitrix and having to learn how to use it. This would completely change the power dynamics in the story.