There could be many people who created such fanfiction. It might be an individual writer who is a big fan of both the Spider - Man and Thor characters and wanted to see what would happen if Peter could lift the hammer. It could also be part of a fanfiction community where different people contribute ideas and sometimes collaborate on stories.
It could be about an alternate scenario where Peter, perhaps Peter Parker from the Spider - Man universe, is somehow able to lift Thor's hammer. This might involve him having to prove his worthiness in a unique situation within the fan - created story.
He might gain new powers or abilities. Since the hammer is a powerful magical weapon, lifting it could unlock some latent potential within Peter. Maybe he can now control lightning like Thor, or he has enhanced strength and durability.
In this fanfiction, it's a really exciting concept. Peter Parker, also known as Spider - Man, is able to lift Thor's hammer. This goes against the normal rules in the Marvel universe where only the worthy can lift Mjolnir. It could be that the fanfiction explores Peter's character in a new light, showing his inner worthiness perhaps through his selfless acts as Spider - Man. Maybe it also has implications for his power level, suddenly having the abilities of Thor added to his own.
One possible plot twist could be that when Peter lifts the hammer, it actually has a negative effect on him. Maybe it starts to corrupt him in some way because he's not fully ready to handle that kind of power. Another could be that it's all a trick by a villain who has somehow enchanted the hammer to make Peter think he can lift it, only to use it against him later.
In the 'percy lifts thor's hammer fanfiction', it could be that Percy is transported to the Norse world by some magic or accident. There, he discovers Thor's hammer. Since he's a hero in his own right from the Greek world, he has the courage and the strength of character to attempt to lift it. When he does, it unlocks a series of adventures. He might have to face off against Norse villains who are envious of his new - found power, and he has to learn how to control the hammer's power, all while trying to find a way back home.
The main characters would be Percy and Thor for sure. Percy is the central figure in this scenario as he does the extraordinary act of lifting the hammer. Thor is important because it's his hammer. Additionally, Odin could be a character. As the All - Father in Norse mythology, he would have a great interest in Percy being able to lift the hammer. And from Percy's side, Grover could be there. He might be the one to provide some comical relief during the intense situations that arise from Percy having the hammer.
In this fanfic, Naruto might gain new powers or a special status. Since Thor's hammer can only be lifted by those worthy, Naruto lifting it could signify his great character. He could use the power of the hammer in battles against powerful foes in the Naruto universe, like Madara or Kaguya.
Well, if Spider - Man lifts Thor's hammer, it would mean he has the worthiness to do so. In the Marvel universe, only those who are pure of heart can lift Mjolnir. So it could imply that Spider - Man is not only a hero in terms of his actions but also in his very essence. It might also give him new powers or abilities related to Thor's powers, like control over lightning perhaps.
In some fanfictions, it could be because Peter has a pure heart. Just like in the MCU, only those worthy can lift Mjolnir. Peter might have proven his selflessness and heroism in a particular situation, which made him worthy enough to lift Thor's hammer.