One common theme is the exploration of their different personalities coming together. Sans is usually depicted as cool and collected while Alphys is more nerdy and anxious. Their relationship often involves Alphys learning to be more confident with Sans' support. Another theme is the use of the Underground setting as a backdrop for their relationship to develop, like dealing with the other characters in that world.
One common theme is the exploration of their friendship. Since they are both characters from the same game universe, many fanfictions build on their potential as friends.
One common theme is friendship turning into love. They start as friends or acquaintances, and as the story progresses, they realize they have deeper feelings. For example, in many fics, they begin by collaborating on something, like a scientific experiment or a community project.
One popular 'sans x alphys fanfic' is 'Underground Bonds'. It beautifully explores their relationship in the unique Underground setting. The story focuses on how their different personalities, Sans' laid - back nature and Alphys' more nervous and geeky side, interact and gradually develop feelings for each other. It has some really heart - warming moments and well - written dialogues that make the relationship seem very believable.
One common theme is friendship. Despite their differences from different AU's, they often form a unique bond.
One common theme is the struggle between good and evil, as Dream Sans is often associated with positive aspects and Nightmare Sans with negative ones. Their relationship in fanfics can explore how they deal with their opposing natures.
Common themes in 'lucy x sans fanfic' include trust - building. In these stories, Lucy and Sans usually start off not fully trusting each other. As the story progresses, they learn to trust one another more. Additionally, the theme of protection is often there. Sans might protect Lucy from various threats in their world, or vice versa, which helps to strengthen their bond and is a key part of many 'lucy x sans' fanfictions.
One common theme is the exploration of friendship. Despite their differences, sans and undyne can form a unique bond in many fanfics. For example, they might start off as rivals but gradually become friends through shared experiences.
One common theme is redemption. Chara is often portrayed as a character in need of redemption, and Sans is sometimes the one who helps them on that path. Another theme is the exploration of different AUs, as it allows for a lot of creativity in how their relationship can develop.
A lot of these fanfics also deal with the theme of redemption. Nagito has his own complex backstory, and when paired with sans, there can be a story of redemption for Nagito. It can be about him finding a new purpose or a way to overcome his past through his relationship with sans. And then there's the theme of discovery. Discovering new things about each other, their powers, and their worldviews.
One common theme is the exploration of good and evil. Flowey has done some rather cruel things, while Sans is often seen as a more 'good' character. Fanfics might play with the idea of Sans trying to redeem Flowey or vice versa.