One key element is Clara's relationship with the Doctor. It's often explored in depth, whether it's their friendship, her role as his companion, or any unspoken feelings between them.
A really interesting Clara Oswin Oswald fanfic is 'Clara and the Lost Worlds'. This fanfic shows Clara exploring different lost worlds that she stumbles upon during her travels. It's full of vivid descriptions of these strange new places and how Clara interacts with the inhabitants. It also has some great character development for Clara as she learns more about herself in these unfamiliar settings.
Obviously, Clara Oswald herself is essential. She is the main character associated with the baby. Then, the Doctor could be a great addition. His relationship with Clara could add depth to the story, especially when it comes to how he reacts to the baby. Also, Clara's friends like Danny Pink could be included. His presence could create some interesting situations regarding the baby, like how he might act as a father figure or a protector.
I'm not sure specifically as I haven't read the book. But it might be about some behind - the - scenes details regarding their relationship or the events surrounding them that haven't been widely known before.
In some fanfictions, there are also platonic pairings where they are seen as brothers - in - arms of sorts. They support each other in their criminal endeavors and protect one another from other threats in Gotham. This type of pairing focuses more on their loyalty and friendship rather than any romantic aspect.
Felix and Oswald interact in a rather complex way. They often start off on the wrong foot. Felix might be more cautious and reserved, while Oswald could be more impulsive. For instance, Oswald might rush into a situation in the ink - filled corridors, and Felix would be hesitant, causing some tension between them.
Oswald Cobblepot x OC fanfiction can be really interesting. It allows fans to explore new relationships and storylines. Usually, the OC (Original Character) can bring a fresh perspective to Oswald's story. It might involve the OC getting involved in Oswald's criminal activities in Gotham, or perhaps being a force for his redemption. There could be a lot of drama, like the OC trying to understand Oswald's complex personality and motives.
One common theme is friendship. Despite their differences, they often form a strong bond in fanfiction. Another theme is redemption. Many stories show them trying to make up for their wrongdoings.