One plot idea could be that Kol kidnaps Caroline because he wants to use her as bait to draw out Klaus. He might think that Klaus has a soft spot for Caroline and will come running to save her. Another idea is that Kol is actually in love with Caroline in his own twisted way and kidnaps her to force her to see his side of things, away from the influence of her friends in Mystic Falls.
If Kol kidnaps Caroline, at first their relationship would be very tense. But as time passes, Caroline might start to understand Kol's motives better. For example, if he kidnapped her because of family issues, she could empathize with him on some level. Their relationship could develop into an unlikely friendship or even something more if Kol shows a more vulnerable side to Caroline.
One common theme is the idea of redemption. Kol often has a bit of a dark past in the Vampire Diaries universe, and in fanfiction, his relationship with Caroline can be a path towards redemption for him. Caroline, with her good - hearted nature, can be the catalyst for this change.
I'm not sure specifically as it depends on the particular fanfiction. It could be a story where a character named Kol kidnaps Bonnie within the universe of the show or book that the fanfiction is based on. Maybe it's part of a complex plot involving magic, power struggles, or personal vendettas.
One possible plot could be that Kol kidnaps Elena to use her as bait for his enemies. He might think that by having Elena in his custody, her friends, especially the Salvatores, would come to rescue her and he could then ambush them. Another idea is that Kol has some sort of vendetta against Elena because of her connection to the doppelganger bloodline. So he kidnaps her to extract revenge on the entire line.
They are a popular pairing because they are both complex characters. Caroline is a strong, independent vampire with a big heart. Kol is a mischievous and somewhat unpredictable original vampire. Their personalities contrast in a way that makes for an exciting dynamic in fanfiction. Writers can explore how Caroline's goodness might tame Kol's wilder side or how Kol can introduce Caroline to a more dangerous and exciting side of the supernatural world.
One popular Kol and Caroline fanfiction is 'A New Beginning'. It delves into a scenario where Kol and Caroline meet under unexpected circumstances and their relationship gradually develops. The story has some great character interactions and a well - paced plot.
The Salvatores, Damon and Stefan, are likely candidates. They have always been protective of Elena and would do anything to save her. They could use their vampire skills and knowledge of Kol's weaknesses to stage a rescue.
It could be that in this 'caroline saves kol fanfic', Caroline is driven by her feelings for Kol. She might be the only one who believes in his innocence in a certain situation. So, she embarks on a journey to prove his innocence and save him from being wrongly punished or killed. For example, if Kol is accused of a crime he didn't commit in the vampire community, Caroline could be the one to find the real culprit and clear Kol's name.