One possible plot could be that Castiel discovers a baby that has some sort of supernatural origin. Maybe the baby is a key to stopping an impending apocalypse. Castiel then has to protect the baby while also dealing with his angelic duties and the reactions of his friends like Dean and Sam.
There's also 'Dean, Castiel and Baby: A New Bond'. This fanfiction focuses on how Castiel, in his new 'baby' form, starts to understand human emotions better through his interactions with Dean. It has a unique take on their relationship and is quite engaging.
One key element is the relationship dynamic. Dean is often portrayed as the protector of baby Castiel. For example, in many stories, Dean will go to great lengths to keep Castiel safe from harm.
Well, it could be about Gabriel abandoning or departing from a baby Castiel. Maybe it explores the reasons behind his leaving, like some sort of mission or a conflict that forces him to go.
The appeal lies in the fact that it combines two very distinct elements - the baby form and the trench coat. The baby form makes Castiel seem more innocent and endearing. We get to see him in a state where he's learning and growing in a different way. The trench coat, on the other hand, is a symbol of his identity as an angel. So, when these two are put together in fanfiction, it creates a whole new set of scenarios and character dynamics that are really fascinating to read about.
Family - like relationships are also prevalent. They are sometimes written as if they were brothers, with Gabriel taking on an older - brother - like role. He might teach baby Castiel about the world, about their angelic nature, and how to use their powers. There could be heartwarming scenes of them bonding over these things.
Obviously, Gabriel and baby Castiel are the main characters. Gabriel is the one who leaves, and baby Castiel is the one left behind.
Castiel first wakes Dean gently from the nightmare. Then he sits with Dean and tells him stories about the great heroes in Heaven. He tells Dean that he is also a hero, and that no nightmare can ever truly harm him because Castiel will always be there to protect him. He strokes Dean's hair softly as he talks, which calms Dean down.
Sam would probably be very protective. He has always been there for Dean, and now with a new addition to the family in the form of a baby, he would see it as his responsibility to keep the baby safe. He might also be a bit of a mentor, teaching the baby about the world of hunting and how to handle different supernatural creatures.
The baby Castiel cartoon often has cute and big eyes, along with a chubby face and innocent expressions.
There's a fanfiction called 'Castiel: Baby in a Trench, Big in Miracles'. It focuses on how even as a baby in the trench coat, Castiel is still able to perform small miracles. The story delves deep into the idea that his power is not related to his physical form but rather his angelic essence. It also shows his interactions with other characters in the Supernatural universe in a very endearing way.