Peter Parker is the main character for sure. In addition to Aunt May and MJ, there could be other characters from the Spider - Man universe. For example, Doctor Strange could make an appearance if the injury has some sort of magical or other - worldly aspect to it. Or perhaps Iron Man's influence could be felt if the story is set in a universe where they have interacted. And let's not forget the Daily Bugle crew, like J. Jonah Jameson, who might be looking for a story about Spider - Man's injury.
The 'Peter Parker Gets Stitches' fanfiction might be centered around the idea of vulnerability. Peter is often seen as a strong superhero, but getting stitches shows his human side. It could be about how he copes with this moment of weakness. There could be a lot of internal monologue as he sits in the hospital or wherever he gets the stitches, thinking about his responsibilities and how this injury might impact his future as Spider - Man.
Well, Mary Jane might be in it. She could be in danger at some point, which gives Peter an extra motivation to save the city. And of course, there could be some new characters created just for this fanfiction, like a young inventor who teams up with Peter to defeat the bad guys. There might also be some villains from the Spider - Man universe, like the Green Goblin or Doctor Octopus.
It could be a vengeful criminal that Spider - Man has put away in the past. This criminal has spent years in prison plotting his revenge and finally gets the chance when Peter is vulnerable. Maybe he manages to ambush Peter in an alleyway while he's on his way home from school or work.
Peter could get a dog. A loyal dog would be a great companion for him, following him around during his daily life and even being a sort of sidekick. It could sense danger and bark to alert Peter when something was wrong.
In addition to the regular characters, there could be some original characters created for the fanfiction. For example, a new friend or a dealer (if the story goes in that direction, without promoting drug use in a positive way). These new characters could add more complexity to the story and help drive the plot forward, whether they are there to help Peter or cause more trouble for him.
In 'Peter Parker gets bullied fanfiction', it might show Peter being bullied online as well. With his secret identity, he has to be careful about how he responds. Some bullies could spread false rumors about him on social media, which affects his relationships at school. This could lead to him feeling more isolated and having a hard time concentrating on his studies and his superhero duties.
Well, in some 'Peter Parker Gets Stabbed' fanfiction, it might happen during a fight with a new, powerful villain. The villain could have a weapon specifically designed to harm Spider - Man, like a blade coated with a substance that weakens his healing factor. Peter might get stabbed while trying to protect someone, like MJ or Aunt May. And then he has to deal with the injury, hiding it from his loved ones while also trying to figure out how to defeat the villain before the wound becomes too much to handle.
In a 'Peter Parker gets a chibi' fanfiction, the chibi could be from an alternate dimension. Peter first thinks it's some sort of strange new enemy but soon realizes it's just a lost little being. He decides to help it find its way home. Along the way, they have all sorts of adventures. The chibi might have unique abilities that Peter doesn't have, like the ability to communicate with animals. This could lead to some interesting situations where they have to work together with the help of the animal kingdom to overcome obstacles.
Peter Parker would be central. Additionally, Doctor Strange could play a role. Since he has knowledge of the future and different timelines, he might try to intervene and prevent Peter from doing the snap. Then there are the villains. Maybe Mysterio, who has a grudge against Peter, could try to manipulate the situation to make Peter snap in a way that benefits him. And of course, Aunt May would be there in some capacity, perhaps as the voice of reason for Peter.
One possible theme could be self - reliance. Peter giving himself stitches might show his ability to take care of himself in a difficult situation.