First, find like-minded collaborators with similar writing styles and interests. Then, clearly define the story's theme and plot together. Good communication is key throughout the process.
Doing a collab story involves a lot of teamwork. You both need to respect each other's ideas and be willing to compromise. Outline the story structure beforehand and take turns writing different parts, while constantly reviewing and editing each other's work.
Well, maybe the collab introduced ideas that clashed with the original essence of your fanfiction. For example, if the other person had a very different vision of the characters or the plot. Their ideas could have forced your story in a direction you didn't like, or they might have made changes that disrupted the flow you had carefully crafted.
Peter would probably be really shocked at first. He might try to quickly explain who he is and that he's not a bad guy. For example, he could start blabbing about being Spider - Man and how he just wanted to meet the Avengers.
One school intruder story is about a person who entered a school with a weapon. The school went into lockdown immediately. Teachers quickly hid students in safe places like closets. Fortunately, the security guards managed to subdue the intruder before anyone got hurt.
Once upon a time, there was an old house on the outskirts of the town. One night, an intruder crept up to it. He was a sneaky fellow, looking for some easy loot. He jimmied open a window and slipped inside. But little did he know, a dog was sleeping in the kitchen. The dog woke up and started barking furiously. The intruder, in a panic, tried to run back out the window but got stuck halfway. The owners of the house woke up, called the police, and the intruder was caught red - handed.