Well, one possibility is that Tony could replace Peter in a mission. Maybe Peter gets injured and Tony steps in to finish what Peter started. It could also be about Tony taking over Peter's role in a social or school setting within the fanfiction world.
In the 'harley replaces peter fanfiction', it could be that Harley steps into Peter's life. For instance, she could start living in Peter's neighborhood and interact with his friends and family. She would then deal with the same kind of threats that Peter has to handle, but with her own brand of problem - solving. She might be more brash or use her engineering skills more directly compared to Peter's more traditional superhero approach.
Obviously, Tony and Peter are the main characters. Tony, with his genius intellect and wealth, and Peter, the young and spry superhero. There could also be other characters like Pepper Potts who might be involved in the story, perhaps trying to mediate between Tony and Peter or having an opinion on Tony replacing Peter.
Well, perhaps in the fanfiction, Tony kidnaps Peter because he believes Peter has some sort of secret that could endanger the world if it gets out. He might be trying to protect the world in his own, extreme way. And Peter is left confused and scared, having to figure out how to convince Tony he's on the right side.
Well, perhaps Tony has some sort of misunderstanding. Maybe he thinks Peter has betrayed him in some way, so he kidnaps Peter. But later, as he realizes his mistake, he tries to make it up to Peter.
It could also be that Tony buys Peter some things for his personal life. Such as some nice clothes or tickets to a cool event. This would be a way to show their bond outside of the superhero world. Tony might see Peter as a son - like figure and want to give him experiences that he missed out on in his own youth.
Well, perhaps it could be about Tony and Peter having some sort of adventure where hiccups play a strange role. Maybe they are in a world where hiccups are a sign of a special power, and they have to figure out how to control it while dealing with some sort of villain. It could also involve them learning about the origin of these hiccup - related powers in their universe.
Well, it could be that Tony, seeing Peter as a son - like figure, leaves him something very special in his will. Maybe it's his high - tech suit technology, which would help Peter continue his superhero journey in a more advanced way.
Perhaps it could involve some sort of magical or scientific experiment gone wrong that results in Tony being able to give birth. Peter could be the result of a genetic manipulation within Tony's body, and the story might then focus on how they adapt to this strange new situation.
Maybe Peter inherits Tony's high - tech gadgets. For example, he could get access to some of Tony's Iron Man tech, which would be a huge deal. This could set him on a new path in his superhero journey, perhaps allowing him to upgrade his own suit or develop new abilities.
One possible plot could be that after an incident, perhaps a spell gone wrong or some kind of memory - wiping event related to Tony's tech. Peter Parker is erased from Tony's memory. Peter, who considered Tony a mentor, is heartbroken when he realizes Tony doesn't recognize him. He tries to jog Tony's memory by showing up at the Stark Tower with his Spider - Man suit, but Tony just sees him as a random kid in a strange costume.