I really liked 'Crossed Paths'. In this fanfic, Castiel gets sent to Mystic Falls by accident. He teams up with Elena and Damon to fight off a group of rogue werewolves that are being controlled by a cross - dimensional witch. It's interesting to see how Castiel's angelic powers are perceived in the Vampire Diaries' world, and how he adapts to deal with the vampires and other supernatural beings there.
One interesting plot idea could be a battle between the hunters from Supernatural and the vampires from Vampire Diaries. Maybe the Winchesters end up in Mystic Falls and think all the vampires there need to be hunted. Another idea is a character swap. For example, Castiel could end up in the Vampire Diaries world and interact with the characters there in a very different way compared to his usual interactions in Supernatural. A third idea could be a joint mission to fight a greater evil that threatens both universes, like an ancient demon that wants to use the power of the vampires in Vampire Diaries and the magic from Supernatural for its own dark purposes.
One great Supernatural and Vampire Diaries fanfiction is 'The Crossover'. It combines the two universes in an interesting way. The characters from both shows interact in a way that feels natural, given their supernatural natures. It has a lot of action and some really cool plot twists.
One common trope is the 'fish - out - of - water' situation. For example, when the characters from Supernatural first arrive in Mystic Falls, they are confused by the different rules of the vampire society there compared to the monsters they usually hunt. Another trope is the 'power - struggle'. This could be between the powerful vampires like the Originals in Vampire Diaries and the angels or demons from Supernatural. They often have to compete or cooperate depending on the situation in the fanfic.
Imagine if Elena Gilbert was somehow connected to an Infinity Stone. This would draw the attention of Thanos, but also the Avengers. The Vampire Diaries characters would have to protect Elena while also dealing with the fact that the Avengers are now in their small town. There could be a lot of mistrust at first, but as they learn more about each other's motives and capabilities, they form an alliance to keep the Infinity Stone out of Thanos' hands.
One common theme is the battle between good and evil. In both shows, there are clear lines between the heroes and the villains, and this is often explored in fanfiction. Another theme is the power of friendship and family. Characters in both shows rely on their friends and family members, and this is also a big part of the fan - created stories.
I think Crowley from Supernatural and Klaus from Vampire Diaries would have a fascinating interaction. They are both power - hungry and manipulative. They could either form an alliance to achieve their own goals or be in a constant battle for control. Also, Dean and Stefan. Stefan is a more 'controlled' vampire compared to Damon. Dean might respect Stefan's self - control to a certain extent, but they would still have differences due to Dean's hunting background. And what about Rowena from Supernatural and Caroline? Caroline is all about her studies and her new vampire life, and Rowena could either be a mentor - like figure or try to use Caroline for her own magic - related purposes.
Well, a frequent theme is the clash of different cultures. In a Vampire Diaries and Harry Potter crossover, you have the magical culture of Hogwarts clashing with the vampire - based culture of Mystic Falls. This can lead to misunderstandings and conflicts that drive the story forward. Also, survival is a big theme. In many crossovers, the characters have to find a way to survive in a new and more dangerous world created by the crossover. For instance, in a Vampire Diaries and Buffy the Vampire Slayer crossover, the vampires from Vampire Diaries might have to adapt to the slayer - filled world of Buffy or face being staked.
A popular one is 'A New Alliance'. In this fanfiction, the plot brings together the different supernatural elements from 'The Vampire Diaries' and 'The Originals' in a unique way. The author does a great job of maintaining the personalities of the original characters while also creating new and exciting storylines. It's a must - read for fans of the two shows.
One great 'Vampire Diaries' crossover fanfiction is 'The Vampire Diaries and Supernatural: The Crossover'. It combines the dark, supernatural elements of both shows really well. The characters from each show interact in a believable way, and the plot keeps you hooked from start to finish.