Well, perhaps they get kidnapped by an alien race that is studying humans with special abilities. Peter's powers as Spider - Man and Flash's unique character traits could be of great interest to them. They could be held in some high - tech alien prison where they have to figure out a way to escape together, forging an unlikely alliance in the process.
In the fanfiction, they might be kidnapped by a supervillain who wants to use them as bait to lure Spider - Man. Maybe the kidnapper thinks Flash has some connection to Peter Parker (aka Spider - Man) and plans to expose his identity through Flash.
It could be that a criminal organization kidnaps them. They might be after Peter's scientific knowledge, thinking he can create some advanced weaponry for them. Flash, on the other hand, is just caught in the crossfire. Peter would then have to use his wits and powers to not only save himself but also Flash, all while keeping his identity a secret.
Maybe it's an old enemy of Peter's who has found out about his friendship with Flash. For example, someone from Oscorp who wants to take revenge on Peter for foiling their evil plans in the past and figures kidnapping Flash will draw Peter out.
A fanfiction could show Peter being kidnapped by a criminal mastermind who wants to use him as leverage against Spider - Man in the future. Peter, as a child, would have to find a way to escape and also figure out how to stop this person from ever coming after him again. It could involve him making new friends among other kidnapped kids who help him in his escape plan.
There could be a deeper reason for the fight in the fanfiction. Maybe Flash has accidentally found out something about Peter's double life and is trying to blackmail him. This would lead to a more intense and emotional fight, with Peter having to protect his secret identity at all costs.
Well, if Peter Parker becomes Flash in fanfiction, he might use his new super - speed in really interesting ways. For example, he could swing between buildings as Spider - Man even faster. Maybe he'd combine his spider - sense with the Flash's ability to see things in slow motion, making him an even more formidable hero. He could also use the Flash's speed to create new web - slinging techniques, like using his speed to make the webs shoot out faster and farther.
Well, one possibility is that Spider - Man's friends, like Ned and MJ, would quickly realize he's missing. They might start their own investigation, using Ned's tech - savvy skills to try and track Peter. Maybe they'd find some clues that lead them to one of Osborn's secret lairs. Another thing could be that Peter manages to break free on his own using his spider - powers and his wits. He could then turn the tables on Osborn and expose his evil plans to the public.
Well, one possibility is that the Avengers will quickly notice Peter's disappearance. Tony Stark might use his high - tech resources to track him down. He could analyze any evidence left behind at the scene of the kidnapping. For example, if Peter's Spider - Man suit has some sort of tracking device, even if Hydra tried to disable it, Stark could find a way to reactivate it or use its last known location to start the search.
Well, they could be kidnapped by a mad scientist. The scientist might be interested in Peter's spider - DNA and Tony's Iron Man suit technology. Once kidnapped, they would first try to assess their situation. Tony would probably look for any weak points in the confinement area, while Peter might use his spider - sense to detect any incoming danger or opportunity for escape.
Maybe Doctor Octopus. He has always been obsessed with power and knowledge. He might kidnap Peter to figure out the secret behind his spider - powers. He could think that by studying Peter, he can enhance his own mechanical arms or gain some new form of power that would make him the most feared villain in the city.
Well, perhaps Flash gets into some sort of trouble like being kidnapped by a group of villains who want to use him as a bait to lure Spider - Man (Peter Parker). Peter, using his spidey - senses, tracks Flash down and has to fight off the bad guys to save him. It could also be that Flash accidentally stumbles upon a dangerous experiment and Peter has to save him from the resulting chaos.
One possible reason could be envy. Flash might be jealous of Peter's intelligence or popularity at school. Maybe he feels overshadowed by Peter and his achievements, so in the fanfiction, his anger and frustration lead him to lash out physically.