The idea of 'forbidden love' is also common. Maybe because of their different natures (Dean being a hunter and Cas being an angel), or because of some external forces like the rules of their respective groups. This adds an extra layer of drama to the story. And of course, there's the theme of pure, unadulterated love where the kiss is just a beautiful expression of their deep feelings for each other.
One common theme is the revelation of hidden feelings. For a long time, they may have been suppressing their emotions for each other, and the first kiss is like the breaking of a dam. Another theme is the acceptance of a new aspect of their relationship. It's not just about being friends or hunting partners anymore. And finally, there's often a sense of new beginnings, as if this kiss opens up a whole new world of possibilities for their relationship.
One common theme is the struggle with their identities. Both Dean and Cas have complex identities and in many fanfictions, their kiss is a moment of acceptance of themselves and each other. For example, Cas coming to terms with his feelings as an angel while having human - like emotions for Dean.
Well, in many Cas and Dean first kiss fanfictions, it often occurs in a moment of high emotion. Maybe after they've just saved each other from a dangerous situation. The writers usually build up a lot of tension between them first. For example, there might be lingering looks and unspoken feelings for a long time before that first kiss. It's a way to explore their relationship deeper than what's shown in the original series.
I really like 'The Kiss in the Rain'. It's a bit of a classic in the dean and cas fanfiction world. The rain - soaked setting for their kiss adds a lot of drama and emotion. The story around it also does a good job of showing how their relationship has evolved over time.
Another theme is the slow - burn romance. Writers often take their time building up the relationship between Cas and Dean. They might start as friends or comrades, and over time, the feelings of love gradually develop. It could involve a lot of longing looks, small acts of kindness that slowly turn into deeper affection.
Another theme is sacrifice. Given the nature of the Supernatural world, they often put themselves in harm's way for each other. Fanfictions play on this selfless aspect of their relationship. For example, Cas might sacrifice his grace to save Dean, or Dean might risk his life to rescue Cas. It shows the depth of their bond.
One popular trope is the 'hurt/comfort' scenario. For example, Dean gets injured on a hunt, and Cas takes care of him, which leads to a tender moment and a kiss. It plays on the emotional bond between them and the protectiveness they feel for each other.
The theme of redemption can also be seen. Dean, with his often troubled past, might find a form of redemption through his relationship with Cas, who represents something pure and good in his life. And Cas, on the other hand, might find a new purpose in his existence through Dean, a way to truly belong in the human world.
The theme of love in different forms is very common. It could be platonic love, romantic love or a love that defies definition. Another is the theme of fighting against the odds. They face so many powerful enemies in the Supernatural world, and how they face these together is a big part of fanfics. Also, the idea of self - discovery is present. Both Cas and Dean are constantly learning about themselves, especially in relation to each other, in many fanfics.
A common theme is protection. Cas, as the 'daddy' figure, often protects Dean from various threats. Another theme is emotional growth. Dean might grow and develop in his relationship with Cas.