Yes, there are quite a few. You can check out fanfiction platforms like Archive of Our Own. There you'll find a variety of stories exploring the relationship between Oz and Gilbert, ranging from angsty tales to more heartwarming ones.
One popular 'oz x gilbert' fanfiction I've come across focuses on their friendship evolving in a unique fantasy world. It shows how they support each other through various challenges. Another one delves into their backstories and how that affects their relationship in the present. There are also some that take a more comical approach, like them getting into silly misunderstandings.
Archive of Our Own (AO3) is a great place to start. It has a large collection of fanfictions for various fandoms, including Pandora Hearts. Just search for 'Oz x Gilbert' in the search bar, and you'll get a list of relevant stories.
Love and friendship are common themes. Their relationship starts as a friendship with a bit of rivalry and then blossoms into love, which is often explored in fanfictions.
In violet x gilbert fanfiction, the theme of acceptance is quite prominent. Gilbert accepts Violet for who she is, with all her quirks and past traumas. And vice versa. Another theme is the power of connection. Their relationship is depicted as something that gives them strength. And the theme of hope also runs through many of these fanfictions, as their relationship is often a source of hope for both of them in a rather difficult world.
One aspect to consider in Gilbert x Violet fanfiction is the exploration of their relationship's growth. Their connection in the original work was complex and filled with unspoken emotions. Fanfictions often delve deeper into how they might communicate better, perhaps in post - war scenarios where they are trying to rebuild their lives. For example, some fanfictions may focus on Violet learning more about human emotions through her relationship with Gilbert, which was a central theme in the original anime.
Overcoming obstacles is also frequently seen. Whether it's social differences, misunderstandings, or external problems, they have to work through these issues to be together. This adds drama and depth to the fanfics, making their relationship more interesting to read about.
It's hard to say without knowing the specific nature of Polly and Oz. But often in fanfic, common themes can be friendship, adventure, or even romance.