One possible reason could be some kind of strange chakra infusion. Maybe he comes into contact with a powerful and mysterious chakra source that mutates his body in a way that causes tails to grow. Another reason might be related to some ancient curse or prophecy. It could also be the result of a new jutsu he attempts that goes wrong and has unforeseen physical consequences.
Yes, in some fanfictions, Naruto is often depicted as having a very special connection to the Nine - Tails that goes beyond the normal relationship in the original story. For example, he might be able to fully control the Nine - Tails' power in ways not shown in the canon, or they could have a mental bond that allows for unique forms of communication and cooperation.
A new character could be introduced as the host. This character could be from a hidden clan with a special ability to bond with the Eleven Tails. They would bring a fresh perspective to the story, and their journey of coming to terms with the power of the beast and its implications in the Naruto universe would be an exciting plotline.
Power is a major theme. The 0 tails often represents a new and mysterious power source. Another theme is discovery, as characters usually discover the existence and nature of the 0 tails. Also, there's the theme of conflict, as the appearance of the 0 tails usually brings some kind of struggle in the Naruto world.
Well, in a fanfiction where Naruto becomes the zero tails, it could open up a whole new world of storytelling. The zero tails has a mysterious origin and nature. Naruto's transformation into it could mean a shift in the power balance in the Naruto universe. His relationships with other characters like Sasuke and Sakura would also be affected. For example, they might be initially afraid or suspicious of his new form. And Naruto himself would need to learn how to use the zero - tails' power for good, perhaps by finding a way to combine it with his existing values and ninja skills.
In fanfiction, Naruto's protectiveness towards the Nine - Tails can stem from multiple reasons. Firstly, he has had a long journey of co - existing with it. They have a symbiotic relationship now. Secondly, Naruto has seen the power of the Nine - Tails and how it can be misused by others. He doesn't want that to happen. He also respects the Nine - Tails as a powerful entity. When it comes to threats against the Nine - Tails, Naruto uses his skills and his bond with it to safeguard it. He might even negotiate with others on behalf of the Nine - Tails to ensure its safety and well - being.
Another unique exploration could be through a shared goal that is not related to the main Naruto plot. For example, they both want to protect a special place in the spirit world that has significance for the Nine - Tails. To do this, they have to work together in a way that they haven't before. Naruto has to use his human skills and the Nine - Tails has to use its tailed - beast powers in harmony. This would show a different side of their relationship, one based on mutual respect for each other's abilities.
In the original Naruto canon, such a concept is completely against the established lore and is not possible. However, in the realm of fanfiction, while there might be some extremely out - there and non - canon ideas, I haven't come across one specifically with this plot. Fanfiction often has very creative and sometimes very strange ideas, but this one seems rather unorthodox and goes against the nature of the Nine - Tails as a powerful chakra - based entity, not a biological being in the traditional sense that can get pregnant.
Sasuke could be a main character in a Naruto 11 Tails Fanfiction. He has always been Naruto's rival and equal in many ways. His skills and knowledge of the ninja world could be crucial in dealing with the 11 - tails. Maybe he would have a different perspective on how to handle the situation compared to Naruto.
One common theme is friendship. The twin - tailed characters often form strong bonds with Naruto and his friends. Another theme could be self - discovery, as the new characters in the fanfiction might be on a journey to find out more about their powers and identities.