They might have an epic celebration. The Straw Hats would be excited to see Shanks, especially Luffy. Luffy would probably challenge Shanks to a friendly duel or just be overjoyed to show him how far he's come. Shanks would be proud of Luffy and his crew, and they could all share stories of their adventures over a big feast.
In the fanfiction, there could be a tense moment at first. The Straw Hat Pirates are a rowdy bunch, and Shanks has his own crew. But then they'd realize they're all on the same side. Shanks might offer some advice to Luffy, like how to better handle the power of the straw hat or deal with stronger enemies. And the two crews could exchange treasures or items that are important to them as a sign of friendship.
Luffy would likely run up to Shanks with a big grin and start chatting non - stop about his adventures. Shanks would listen with a smile. The rest of the Straw Hats would be a bit more reserved at first, but then they'd join in. Sanji might offer to cook for everyone, which Shanks would surely appreciate.
One great rival could be a character with a powerful Devil Fruit ability. For example, a character who has a Logia - type Devil Fruit that allows them to turn into a natural element like lightning. This would make them very difficult to defeat in combat as they could dodge attacks easily. They could also use their element - based powers to attack the Straw Hat Pirates in unexpected ways, such as sending bolts of lightning towards their ship.
Luffy and Zoro's bond would still be strong. Maybe in a reincarnated life, they meet as rivals at first in a martial arts tournament but soon realize they share the same goals and become partners again. Nami and Usopp could be siblings in their new lives, with Nami being the protective older sister and Usopp using his creativity in a new family dynamic.
Luffy would be furious. He'd immediately set out to rescue Sanji without a second thought. He'd probably charge straight at Doflamingo's stronghold without a proper plan at first, just driven by his anger and determination to get his crewmate back.
Well, it depends on the setting of the fanfiction. If it's a steampunk world, Luffy could be a daredevil pilot with his stretchy body helping him in acrobatic flying. Zoro might be a mechanical swordsman, with his blades enhanced by steam - powered technology. Nami could be a navigator on an airship, using her knowledge of winds and weather in a whole new dimension.
One popular trope is the 'lost relative' trope. For example, the OC could be a long - lost relative of one of the Straw Hat Pirates. Another is the 'powerful newcomer' trope, where the OC has some extraordinary power that helps the crew in a difficult situation. There's also the 'love interest' trope, although this can be a bit overdone. The OC might fall in love with one of the pirates or vice versa.
Well, Naruto's skills like his shadow clones could be a great asset. He could use them for various tasks on the ship, from cleaning to helping in battles. His determination would also match the Straw Hats' spirit.
First, understand the Straw Hat Pirates' personalities well. For example, Luffy's carefree and determined nature. Then, create an OC (Original Character) that can interact meaningfully with them. Maybe the OC has a special skill or a unique backstory that ties into the pirates' adventures. Think about how the OC can join their crew or be an ally in their journey.
Another scenario could be that Hancock's presence causes some internal conflict within the Straw Hat crew. Nami might be a bit wary of her because of her past actions and power. Chopper could be curious about her Devil Fruit abilities. Zoro might not trust her easily. However, in the face of a common enemy, they would have to put aside their differences and work together. Hancock might learn a lot from the Straw Hat crew's camaraderie and freedom - loving spirit, which could change her perspective on pirates in general.
When it comes to navigation, Nami would be interested in Kenway's knowledge of different sea routes and hidden islands. Kenway could learn from Nami about the unique weather patterns in the One Piece world. Also, Chopper would be curious about Kenway's health and any medical knowledge he has from his time as a pirate. Kenway, in turn, would be entertained by Chopper's cute and innocent nature.