In a fanfiction scenario, it could be part of a plot to create some drama. Maybe there's a villain who has a mind - control device and made them forget on purpose. This would lead to Tony feeling hurt and left out, which could then drive the story forward as the Avengers try to make it up to him and also deal with the threat of the villain.
Tony would probably be really hurt. He's a human after all, despite being a genius billionaire playboy philanthropist. Birthdays are special, and for his friends to forget would sting.
One possible plot could be that Tony makes a great sacrifice during a battle but the Avengers, due to some mind - altering spell or extreme shock, forget all about him. Tony wakes up alone, injured, and has to figure out how to deal with his new situation while also trying to find a way to make the Avengers remember him again.
It could be Loki. He might have some new trick up his sleeve where he makes the Avengers forget Tony as part of a bigger scheme to cause chaos among the team and weaken their defenses. He could be planning to take over the world while the Avengers are distracted by this strange memory loss.
In this kind of fanfiction, the rogue Avengers might feel remorse. As they watch Tony's memories, they could see the events from his perspective. Maybe they realize how their actions had a negative impact on him and the team. They might start to question their own motives and decisions that led to the rift among them.
One possibility is that Tony is extremely good at keeping his identity a secret. He might have used advanced technology to disguise his Iron Man activities so that the Avengers don't notice any connection. For example, he could have created hidden bases and used undetectable communication channels. Also, Tony may act so differently as Iron Man compared to his normal self around the Avengers that they just don't suspect it's him. He might be more confident and bold as Iron Man, while being more laid - back and sarcastic as Tony Stark among the team.
Perhaps they'll be so into the fanfictions that they'll try to incorporate some of the fictional elements into their real lives. For example, if there's a fanfiction where Tony has a unique way of powering up his suit, they could try to replicate it in a way that's applicable to their own tech. It could also strengthen their bond with Tony as they get more insights into his character through these fictional works.
In this fanfiction scenario, Peter himself would likely go through a lot of changes. He might feel a new sense of pressure, knowing that he is now seen as Tony's son by the Avengers. He could also feel more accepted into the group, like he truly belongs. There could be heart - warming moments where the Avengers share stories about Tony with Peter, helping him to understand his father better and grow into his own as a hero.
In fanfiction, if the Avengers meet Tony's wife, it could be a really heartwarming scenario. They might have a big gathering at the Stark Tower. His wife could befriend the Avengers easily, sharing stories and making everyone feel at home. Maybe she'd cook for them all, and they'd exchange tales of their adventures.
In this kind of fanfiction, the Avengers might gain a deeper understanding of Tony. They could see his past traumas, his creative processes, and the moments that shaped him into the man he is. It might lead to them having more empathy for his actions and decisions.
In such a fanfiction, the Avengers might be very protective of Tony's daughter. They could teach her self - defense skills or share their heroic stories with her.