The other characters' reactions could be quite diverse. Flash's friends might be supportive at first, thinking it's just a new hobby of his. But as his pretense continues, they might start to get annoyed. The bullies in Flash's clique could see it as a weakness and start to pick on him. Meanwhile, the people who are actually Spider - Man fans might be outraged that Flash is faking it just for attention. They could confront him and expose his falsehood, leading to a big drama in the story.
Well, if Flash pretends to be a Spider - Man fan in a fanfic, the characters' reactions would depend on their personalities. Gwen Stacy, if she were in the story, might be sympathetic at first, thinking Flash is just trying to fit in. But as she realizes he's being false, she would be disappointed. Harry Osborn could use Flash's pretense to his advantage, perhaps getting Flash to do things for him in the name of Spider - Man. And the Daily Bugle crew would see Flash as a potential source of a story, either making him a hero for his 'love' of Spider - Man or trying to expose him as a fraud.
Well, the plot could be that Flash, who is usually a bit of a bully, suddenly decides to pretend to be a huge Spider - Man fan. Maybe he does it to impress a girl who loves Spider - Man. He starts dressing up like Spider - Man in a really comical way, with a homemade suit that's all wrong. He might try to do Spider - Man - like stunts but fails miserably every time, creating a lot of chaos and humor in the story.
Some would be inspired. Characters like All Might might see Peter Parker's journey as similar to his own in some ways. Both are trying to do good in a world full of challenges. All Might could appreciate Peter's determination to protect his city despite having a normal life outside of being a hero.
The Avengers would be very concerned. Captain America would immediately take charge of the situation, trying to keep everyone calm while they assess Spider - Man's injuries. Iron Man would start scanning for the best way to treat him, using his high - tech equipment. Thor might offer some of his Asgardian knowledge of healing, if there was any. Black Widow and Hawkeye would be on guard, making sure there were no further threats while the team focused on Spider - Man.
Spider - Man would probably be shocked at first. He looks up to the Avengers and being kidnapped by them would be the last thing he expects. He'd likely try to talk his way out, using his quick wit and charm. He might start by asking why they're doing this and try to convince them that they've made a mistake.
Spider - Man would be very confused. He would feel betrayed because he thought the Avengers were heroes he could trust. He could start by asking them why they are doing this. If they don't give him a satisfactory answer, he might try to escape in a sneaky way, using his spider - like abilities to find a weakness in their capture setup while still trying to reason with them.
Spider - Man would probably be defensive at first. He's used to working alone most of the time, and being interrogated by the Avengers would seem unfair to him. He might crack some jokes to ease the tension, but also firmly state that he's a hero too.
They could be shocked. Some of the fanfiction might have really wild ideas that they've never thought of.
The characters would have a range of reactions. Barry (Flash) would probably be very protective. He's a hero who helps people, and Kara is his friend. He'd likely offer his speed and any resources he has to keep her safe. Kara's friends on Supergirl's side, like Alex, would be shocked at first but then become very supportive. They might start planning how to protect Kara and the baby from all the threats they face in their world.
They'd likely be intrigued. Batman would study it for plot devices and character development. He might use some of the ideas in his own crime - fighting strategies. Superman would probably be entertained, seeing it as a new form of storytelling about a hero. Wonder Woman might view it as a cultural phenomenon and think about how it reflects on modern society's view of heroes.
They would probably be very intrigued. RWBY is used to their own fantastical world, and seeing the world of Spider - Man through fanfiction would be a new and exciting experience.