In most of these fanfictions, Stiles first reacts with shock. I mean, being kidnapped out of the blue is no small thing. But then he quickly tries to analyze the situation. He might start looking for weaknesses in Peter's setup or try to figure out Peter's motives. He often uses his sharp mind to try and find a way to escape or at least gain some sort of advantage over Peter. In some cases, he also tries to appeal to Peter's better nature, if there is one, by talking about things like morality and the consequences of his actions.
Stiles usually reacts with a mix of fear and defiance. He's afraid because he's in a dangerous situation, but his strong - willed nature makes him defiant. For example, in many fanfictions, he'll shout at Peter, trying to show that he won't be easily broken.
Stiles' reaction is complex. At the start, he's likely to be terrified, especially if he's alone and at Peter's mercy. However, as time passes, his survival instincts kick in. He could start to play mind games with Peter. He might pretend to be more compliant than he really is to lull Peter into a false sense of security. And he'll always be thinking about his friends and how they might come to his rescue. He'll try to leave clues if possible, or at least not do anything that would make it harder for his friends to find him.
He could use his intelligence to manipulate Kate. Maybe he convinces her that he is more useful to her if he is free, and she lets her guard down long enough for him to make a run for it. Also, he could have some hidden skills or knowledge that he uses to break free. Say he knows a spell or a code that unlocks his restraints or the door to his prison.
Stiles might initially be shocked. He has been a part of the pack for a long time, and Scott kicking him out would be completely unexpected. He could stand there in disbelief, unable to process what has just happened.
There's a fanfic called 'Peter's Kidnapped Prize'. It starts with a very intense kidnapping scene. As the story progresses, it shows how Stiles' friends are trying to find him, and at the same time, Stiles is trying to survive in Peter's clutches. 'Stolen by Peter' is another one. It's unique in the sense that it shows a different side of Peter, not just as a villain but as a complex character with his own reasons for kidnapping Stiles. 'The Kidnapping of Stiles' also stands out as it weaves in some elements of mystery about why Peter chose Stiles in particular.
It could be that Stiles is in some kind of danger, perhaps from another supernatural being. And he goes to Peter because Peter has certain powers or knowledge that could protect him. For example, Peter might know how to defeat a particular enemy or how to get out of a tricky situation involving magic or some other supernatural element.
Some of his friends might be really surprised. Scott, for example, might be a bit worried that Stiles' vampire obsession could lead him into dangerous situations. Lydia, on the other hand, could be more intrigued and might want to know more about the fanfiction. She might see it as an interesting intellectual pursuit.
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.
Another possibility is that Stiles is there because of a sense of obligation. Perhaps Peter has done something for Stiles in the past, like saving his life or helping him out of a difficult situation. So, Stiles feels like he owes it to Peter to visit him in the hospital and make sure he's okay.
It could be a rogue werewolf. Maybe this werewolf has a grudge against Stiles' pack and thinks that by kidnapping Stiles, he can get some sort of revenge or leverage.
There's a fanfiction where Stiles is kidnapped by a supernatural being and tortured in a hidden lair. It focuses on his attempts to escape and the friendships that help him through it. The author does an excellent job of building tension throughout the story.
The portrayal of their friendship varies. Sometimes, it's a friendship that defies the odds. Given Peter's actions in the original story, it's unexpected for him to be friends with Stiles. But in fanfiction, they can bond over their love for the supernatural world. They might go on adventures together, relying on each other's skills. Stiles' logical thinking and Peter's instincts can make them a great team. And as they spend more time together, their friendship deepens, with them learning to trust each other more and more.