One common theme is forbidden love. Maybe a vampire falling in love with a werewolf in the academy, which goes against the norms of their species. Another is the underdog rising to power. A student who is initially underestimated but then discovers some great power within themselves.
In 'supernatural fanfiction', a frequent theme is the alternate universes. Writers like to imagine different versions of the 'Supernatural' world, where things happened differently. Romance is also a big theme, whether it's between the main characters or new characters introduced in the fanfic. Also, the origin stories of the supernatural beings are often explored, giving more background and depth to the existing lore.
One common theme is power struggle. Abaddon is a powerful demon, so many fanfictions explore her battles for power, either against other demons or the Winchesters. Another theme is her backstory. Writers often delve into her past to give more depth to her character.
One common theme is redemption. Since Adam had a rather rough deal in the show, a lot of fanfictions explore his journey towards redemption. Another is family. How he fits into the Winchester family dynamic, whether it's forming a bond with Sam and Dean or finding his place in the larger family of hunters.
One common theme is redemption. Cassiel has made some mistakes in the show, and in fanfictions, writers often explore his journey to redeem himself. For example, he might try to make up for his actions by helping Sam and Dean in a more selfless way.
One common theme is the aftermath of the events in the episode. Writers often explore how the characters deal with the consequences. Another theme could be the relationships between the characters, like Dean and Sam's bond, which might be further developed or tested in the fanfictions.
One common theme is redemption. Ketch has done some not - so - great things in the show, and in fanfiction, he often gets a chance to redeem himself. For example, he might help the Winchesters in a big way to make up for his past actions.
Character pairings are also a big theme. Some fanfictions might pair characters like Elsa with Dean, exploring how their different personalities and powers interact. There could be a story where Elsa's ice powers are seen as a form of magic that the 'Supernatural' characters have to either understand or combat. It often involves a lot of relationship building and character development within this unique crossover setting.
Many fanfics focus on the supernatural elements that were present in the episode. They might expand on the lore introduced in 14x14, or they could bring in other supernatural creatures or concepts from the broader Supernatural universe. Writers often use these elements to create more complex and engaging stories, delving deeper into the world that the show has created.
One common theme is the family bond between Sam and Dean. A lot of fanfics explore this further, like how they support each other through tough times. Another is the fight against the supernatural creatures, but with different twists and turns than in the show.