One common theme is self - discovery. The OC often has to figure out their place in the Naruto world while being in a harem, which helps them grow as a character.
One popular 'Naruto oc x harem fanfic' is 'The OC's Adventure in Naruto's Harem'. It has an interesting plot where the original character gets involved with multiple characters from the Naruto universe in a unique way.
A common theme is the OC's integration into the Naruto world. Since the OC is not part of the original story, the fic often focuses on how they fit in, especially in a harem context. Another theme is the development of romantic relationships. With multiple characters interested in the OC, there's a lot of exploration of different types of love and attraction.
Friendship is a common theme. Since My Little Pony is all about friendship, in these fanfics, the OC forms friendships with the members of the harem which often develop into something more. Another theme is self - discovery. As the OC navigates this new world and relationships, they learn more about themselves.
To write a male oc x harem fanfic, you need to focus on character development. The male OC should be multi - dimensional. He could have flaws like being a bit stubborn but also great qualities. For the harem, think about different relationships. Some might be friends - turned - lovers, others might have an instant attraction. Also, use dialogue effectively. The conversations between the male OC and the harem members can reveal their feelings and move the story forward.
One common trope is the 'fish out of water' situation. The OC, being new to the RWBY world, has to navigate through it while attracting the attention of multiple characters for the harem. Another is the 'power - attraction' trope where the OC's unique powers or skills make them appealing to the RWBY characters.
A very frequent trope in 'naruto male oc harem fanfic' is the 'love - at - first - sight' or 'instant attraction' trope. The female characters in the harem often quickly become interested in the male OC for various reasons, whether it's his looks, his power, or his mysterious background. Also, the 'rivalry for the OC's affection' is common. Different female characters in the harem may compete with each other, which adds drama to the story.
Sakura could be one of the likely characters. She has a long - standing relationship with Naruto in the original series. In a fanfic with this concept, she might be drawn to Naruto's new connection with the fem Kyuubi out of curiosity or her own feelings for Naruto evolving. Hinata is also a strong candidate. Given her long - held feelings for Naruto, she would likely be part of the harem, especially as Naruto's power grows with the fem Kyuubi. And Ino could be there too. She's competitive and might see Naruto's new situation as something interesting and want to be part of it.
One common theme is adventure. Since it's set in the One Piece world, the OC and the harem usually embark on various adventures together, exploring new islands and facing off against villains. Another theme is romance, of course, as the OC forms relationships with multiple characters. And there's often the theme of self - discovery, where the OC learns more about themselves and their place in this wild world.
There's also 'The OC's Harem Quest in Ponyville'. In this fanfic, the OC has unique abilities that draw the attention of various ponies in Ponyville, leading to the development of a harem around them. It's full of interesting character interactions and adventures.