One common theme is self - discovery. Female OCs often start out not knowing their true potential and then through their adventures in the One Piece world, they learn about themselves. For example, they might discover hidden powers or talents.
A prevalent theme in One Piece Fishman OC fanfiction is the pursuit of power. The OC fishman often wants to become stronger, either to protect their own kind or to achieve personal goals. This can involve training with unique fishman techniques or seeking out powerful treasures. Also, friendship is a common theme. Just like in the main One Piece story, the Fishman OC forms bonds with other characters, which can be humans, other Fishmen, or even different species. These friendships help them grow and face challenges. In some fanfictions, there's also the theme of redemption, where a Fishman OC who has made mistakes in the past tries to make amends.
A third common theme is the relationship with pirates. In OC Marine One Piece fanfiction, the interactions between the OC Marines and pirates can range from intense battles to unexpected alliances. Sometimes, the OC Marines might learn something from the pirates about freedom or the true nature of the world, which challenges their beliefs as Marines. This creates a lot of interesting storylines and character development.
Another theme is the search for family. Since Whitebeard's crew is like a big family, the OCs often find a sense of belonging within the crew. They might have had a rough past without a proper family, but with Whitebeard's crew, they finally have a place to call home. This is explored in a lot of fanfictions through the OC's journey of self - discovery and acceptance within the crew.
One common theme is adventure. Since One Piece is all about adventure, many fanfictions with Shirahoshi OCs involve her going on new quests or exploring uncharted areas in the One Piece world.
Many 'One Piece Robin x OC fanfiction' works explore the theme of acceptance. The OC, being an outsider in the One Piece world, has to be accepted by the characters, especially Robin. And Robin, with her own past, also has to accept the presence of this new character in her life. There's also the theme of growth, both in terms of power and character, for both Robin and the OC as they interact and go through various experiences together.
One common theme is adventure. Since One Piece is all about adventure, the OC usually embarks on various adventures in the world of One Piece while building their harem. Another theme is the development of relationships. There's the building of romantic and sometimes platonic relationships between the OC and the harem members.
In One Piece Big Mom OC fanfiction, a frequent theme is survival. Big Mom's world can be a dangerous place, and OCs have to figure out how to stay alive. There's also the theme of discovery. The OC might be exploring new parts of Big Mom's territory or uncovering secrets about her past. And the theme of friendship can be found too. The OC could form bonds with other characters in Big Mom's crew or even with those who oppose Big Mom. For instance, an OC might become friends with a character who wants to escape Big Mom's rule.
Power discovery is a common theme. OCs often start off not fully understanding their Devil Fruit powers and have to learn through trial and error.
One common theme is adventure. Since it's set in the One Piece world, the OC and Thatch often go on adventures together. Another theme could be love and friendship, as their relationship is explored.
Common themes include exploration. The OC explores not only the physical world of One Piece but also the complex relationships in the harem. Cultural differences can be another theme. The OC might come from a different background and has to adapt to the unique cultures in One Piece. And finally, the theme of loyalty. The OC has to show loyalty to the harem members and vice versa for the relationships to work.