It could affect Sam a great deal. With Castiel around Dean earlier, Sam might feel a bit left out at first. But then he could also learn a lot from Castiel, like more about the angelic lore, which would help him in his own research.
The villains in the story, such as demons, would also be affected. With Castiel in Dean's life sooner, they might change their strategies. They could be more afraid of approaching Dean because of Castiel's protection. Or they might try to find ways to drive a wedge between Dean and Castiel earlier in the story to gain an advantage.
Perhaps in the fanfic, Castiel starts to accompany Dean on hunts sooner. This could lead to some really cool action scenes where Castiel uses his powers in new and unexpected ways to help Dean defeat monsters. And their relationship could develop in a more intense and different way compared to the original story.
In dean - castiel relationship in such fanfiction, there's often a deep emotional connection. They might show a side of extreme vulnerability towards each other. Their relationship can be intense, with a lot of passion and a sense of 'destined to be together' kind of feeling.
In many fanfics, Castiel's actions and decisions can create tension between Sam and Dean. For example, if he takes a side in an argument between them, it can drive a wedge. But on the other hand, he can also be the glue that holds them together when facing a common enemy. His loyalty to both of them in different ways shapes their interactions.
Castiel is a complex and fascinating character in Sam and Dean's brother fanfic. He often serves as a sort of guide or protector for the brothers. His angelic nature gives him a unique perspective that contrasts with the more human viewpoints of Sam and Dean. He can be both aloof and deeply caring, which makes for interesting character dynamics.
A popular one is 'Wings and Leather'. It focuses on how Castiel's angelic nature and Dean's more rough - and - tumble hunter side complement each other. The fanfic shows their journey together, facing various challenges and growing closer as they do so. It's full of great action scenes as well as some really tender moments.
One common theme is loyalty. They are always there for each other in most fanfics, no matter what the situation is. Another theme is the struggle between the human and the supernatural world as Castiel is an angel and Dean is a human hunter.
Typically, in dean castiel lemon fanfic, there would be a focus on the relationship between Dean and Castiel. The 'lemon' aspect might imply some more intimate or romantic scenes. However, different authors may write with different tones. Some might emphasize the emotional connection between the two characters while incorporating the physical aspect more subtly, while others could be more direct.
Castiel's relationship with his powers might also change. He may have to limit his use of angelic powers to protect the unborn entity. This can cause internal conflict as he is used to using his powers freely. At the same time, it can also show his growth as a character, as he is willing to sacrifice some of his power for the sake of something new and precious.
Some fans would be extremely shocked and heartbroken. Dean and Castiel have a very complex and beloved relationship in the fandom, so seeing Castiel kill Dean would go against what many fans hope for in their relationship. They might be very vocal about their disappointment.
There are also times when Dean's brash actions can wound Castiel. Say, Dean goes off on a dangerous mission without including Castiel, when Castiel has always been there for him. This makes Castiel feel like he's not an important part of Dean's life. In fanfictions, these situations are used to show the vulnerability of their relationship and how much they both need to work on communication and trust.