One popular theme is Castiel's relationship with other characters, such as his loyalty to Dean and Sam. Another is his struggle with his angelic nature and his growing understanding of humanity.
Redemption arcs are also quite common in archangel castiel fanfic. Given some of the things he has done in the series, writers often explore how he tries to make up for his mistakes and find a place for himself in the world, whether it's among humans or with his fellow angels.
A lot of fanfictions focus on the idea of Castiel being different from other angels because of his connection to the Winchesters. There are themes of forbidden love, like a romantic relationship between Castiel and an archangel which goes against the angelic rules. Also, the exploration of Castiel's true purpose and how it relates to the archangels' plans is a big theme.
Definitely. The 'Castiel is an archangel' fanfics are popular among Supernatural fans. They usually offer unique interpretations of the story. For example, they might show how Castiel's new status as an archangel affects his friendship with Dean and Sam. They can also introduce new plotlines and conflicts based on his enhanced abilities.
One popular plot twist could be Castiel secretly being an archangel all along but having his memories wiped. It adds a whole new layer of mystery to his character. Another could be that he is an archangel in a parallel universe and gets switched with the Castiel in the main universe. This can lead to some really interesting character interactions.
One popular theme is the 'friends to lovers' trope. It shows the progression of their relationship from just being comrades in the fight against the supernatural to falling in love. Another is the 'hurt/comfort' theme, where one of them gets injured or is in emotional distress and the other provides support.
You can try some popular fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfics related to various characters, including Archangel Castiel. Just use the search function on the site to look for specific stories.
One of the main things is the exploration of his character. When Castiel is an archangel, it's not just about his powers. It's about how his identity changes. Does he still feel the same loyalty? How does he view his purpose now? Fanfics can dig deep into these aspects. They can also show how his new form affects his appearance and how other characters react to this change. This all combines to make the 'Castiel is an archangel' fanfics really interesting.
Another theme is their relationships with humans. For example, an archangel might form an unlikely bond with a human character, and the fanfic delves into how that relationship develops and affects both parties. It can be a romantic relationship or a more platonic mentorship - like bond.
Another theme is Castiel protecting the reader from various threats, whether it's angels, demons or other dangerous entities. This can lead to a lot of emotional and romantic moments as the reader realizes Castiel's devotion.
Another theme is the redemption arc for Castiel. In these fanfictions, Dean plays a crucial role in helping Castiel find his way back from any dark paths he may have tread. For example, some stories show Dean standing by Castiel during his struggles with his angelic nature.
One popular theme is the sister's relationship with her archangel brothers. It could be about her trying to fit into their world or dealing with their overprotectiveness. Another theme is her own powers and how she discovers and controls them in the context of the Supernatural universe.