At the start, Peter would be in disbelief. But as time goes on, he'd start to get angry. He'd feel betrayed by Tony. Peter would start to plan his escape, using his intelligence and his spider - sense. He'd be constantly on the lookout for any weakness in Tony's setup, all while trying to understand Tony's motives for kidnapping him.
Peter would probably be really confused at first. He looks up to Tony, and suddenly being kidnapped by him would be a huge shock. He might try to talk to Tony, asking him why he's doing this.
Peter would likely be defiant. He has a strong moral compass and wouldn't easily give in to Osborn's demands. He'd probably try to find a way to escape right away, using his spider - abilities like climbing walls and his super strength to break free from any restraints.
Peter might be initially shocked and a bit scared. After all, Tony is like a mentor to him. But then he could become defensive, trying to explain his actions or point of view.
Maybe Pepper Potts could find out what Tony has done and rescue Peter. She might be able to talk some sense into Tony and make him release Peter.
Peter could respond with a bit of humor. He might make a joke like 'I'm not a baby, Mr. Stark, I can handle myself!' while secretly enjoying the affectionate name. This would show his growing confidence in his relationship with Tony, being able to tease him back.
Peter might be embarrassed at first. He's been idolizing Spider - Man and now Tony, a real - life hero - like figure, knows about it. But then he realizes that Tony could be an even greater source of knowledge and support, so he becomes more open about his love for Spider - Man.
Peter might be really nervous at first. He's used to being just the friendly neighborhood Spider - Man, and now the Avengers know he's Tony's son. He could be worried about living up to their expectations.
Peter is likely to be in awe. He might be a bit nervous at first, but also extremely excited. He has looked up to the Avengers for a long time, so meeting them would be like a dream come true. He would probably be stuttering a bit as he tries to introduce himself and show his respect.
Perhaps Peter is a bit annoyed at first. He's trying to focus on class and here's Tony calling. But then when he realizes it might be something important, he starts to pay more attention to the call, all while being cautious not to get caught by the teacher.
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.