I'm not sure specifically as there could be many different interpretations in such a fanfiction. It might involve a character named Rito facing a stabbing incident, perhaps in a battle, a crime scene, or a situation of betrayal.
One possible plot could be that Zoro, turned into a girl, has to deal with the different reactions of his crewmates. Some might be shocked, some might tease him. And he has to learn to adapt to his new physical form while still maintaining his tough fighting spirit.
Well, perhaps an enemy uses a magic spell to turn Zoro into a baby as a way to weaken the Straw Hat Pirates. At first, the crew is in chaos trying to deal with a baby Zoro. But as time passes, they see that baby Zoro has a pure sense of determination. He still tries to train, albeit in a very clumsy and cute way. And in the end, they go on an adventure to find the antidote to turn him back, with lots of comical and touching moments along the way.
It could be a rogue angel. There are always some angels in the Supernatural universe who oppose Castiel's ideas or actions, and they might see stabbing him as a way to get rid of him or send a message.
In such fanfiction, characters might show shock. For example, Dean could be horrified when he sees Castiel stabbed, his eyes wide open and his face pale.
Well, in 'naruto gets stabbed fanfiction', it could be that Naruto is exploring a new and dangerous area where he encounters a powerful and hostile ninja. In the heat of the fight, this ninja manages to land a stabbing blow. It might also be that Naruto is weakened due to some prior injury or chakra depletion, making him more vulnerable to being stabbed by a regular enemy. And, there could be a situation where Naruto is under the influence of some sort of genjutsu that impairs his ability to defend himself and thus gets stabbed.
Perhaps he gets stabbed as a part of a plot to take over his company. His rivals could be behind it, seeing his success as a threat. In the fanfiction, this could lead to a great revenge story where Kaiba has to regain his power and seek justice.
It might be a jealous rival. If Sakura is popular or has something that others envy, like a special talent or a relationship, a rival could have stabbed her out of envy.
I think Zoro's core personality of being tough and fearless would remain. However, being in a female body might make him a bit more aware of certain things, like how he's treated differently by some people. But overall, he'd still be the same Zoro who doesn't back down from a fight and is always looking to improve his skills.