Restoration is also a theme. Castiel is often in a weary state in the series, so in fanfics about his sleep, it can be a time for him to regain his strength, both physically and mentally. His sleep is seen as a way to heal from the many traumas he has endured throughout his time on Earth, whether it's from battles with demons or the internal struggles within the angelic hierarchy.
One common theme is vulnerability. When Castiel is sleeping, he is in a state where he is unguarded, and fanfics often explore how this vulnerability affects him and those around him.
Another theme is the mystery of his dreams. Since Castiel is an angel, his dreams might be different from human dreams. Fanfics like to play with this idea, showing his dreams as visions of other realms or prophecies. For example, some fanfics depict his dreams as glimpses into the future of the Winchester brothers' battles.
Love and friendship are also very common themes. Whether it's a platonic love or a more romantic love, it's often explored. In some fanfics, they have to hide their feelings from others, which adds an element of secrecy. And then there's the theme of sacrifice. They are both willing to sacrifice themselves for the greater good and for each other.
Rescue scenarios are also popular. Other characters, usually Dean, might come to his rescue. This can create a lot of tension and drama in the story. It can also be a way to explore the bond between Castiel and the rescuing character, with a lot of emotional moments as they reunite.
One common theme is Castiel's struggle with his angelic nature. He often has to balance his loyalty to heaven and his newfound connections with humans.
Another theme is self - loathing. In 'castiel depressed fanfic', he frequently blames himself for things that have happened, whether it's his actions in battles or his perceived failures in protecting others. This self - loathing is a big part of his depressive state.
The theme of self - discovery is also prevalent. As a female Castiel, she has to figure out her place in the world, both as an angel and as a female entity. This often involves her coming to terms with her new identity, learning about her powers in a different context, and finding her role in the fight against evil in a more female - centric way.
Reflection is also a big theme. Castiel has a long history, and on his birthday, he may look back on all the things he has been through, the people he has met, and the choices he has made. This can add a lot of depth to the fanfic and make readers understand his character better.
The theme of sacrifice also pops up a lot. Castiel may have to sacrifice his angelic duties or powers for his wife, or the wife might sacrifice her own safety or desires for Castiel. This creates a sense of drama and emotional depth in the stories. For instance, in one fanfic, the wife gives up her chance at a normal life to stay with Castiel in the dangerous world of angels and demons.
One common theme is redemption. Since Castiel has made some mistakes in the show, a lot of fanfiction focuses on him trying to make up for those. Another theme is his relationship with the other main characters, like Dean and Sam. His loyalty and how it is tested is often explored.
There can be a theme of spiritual discovery as well. In some fanfics, his blindness is seen as a way to connect more deeply with the spiritual realm. It can be a way to show that there are other ways to 'see' beyond physical sight, and it adds a really interesting layer to his character.
A common theme is the power struggle. Castiel is often seen as a more 'pure' angel, while Lucifer is the rebellious one. Their interactions are filled with this underlying battle for dominance or influence. Another theme is redemption. Sometimes Lucifer is portrayed as having a chance at redemption, with Castiel being a key factor in that.