Sasuke would probably be initially skeptical. He'd think Naruto was up to some strange new form of training or just being his usual odd self. But if he saw that Naruto's singing of Breaking Benjamin songs actually had an effect, like inspiring the other villagers or giving them courage in a difficult situation, he might start to respect it a little more.
If Naruto was caught singing fanfiction in the village, there would be a whole range of reactions. The merchants in the village might see it as a new opportunity to create merchandise related to this new 'Naruto - singing - fanfiction' thing. The ninja families might be more concerned about whether this is a sign of Naruto getting distracted from his duties. The children would likely be the most excited, running around and telling everyone about it. The village elders, on the other hand, would probably have a long discussion about whether this is an appropriate behavior for someone of Naruto's standing. But in the end, Naruto's charm and popularity would probably smooth over any major negative reactions.
The common people of Camelot would be delighted. They are used to seeing Merlin as the friendly servant, and now he is singing such a beautiful song. They would gather around him, their faces lit up with joy. For the magical creatures in the surrounding forests, they would be drawn to the magic in his voice. Some might come closer to Camelot than they usually do. Some might even try to communicate with Merlin, believing that he is a kindred spirit. This could cause some chaos as the people of Camelot might be afraid of these strange creatures approaching, but also lead to a new understanding between the two worlds.
On the other hand, there would be fans who would welcome it. Maybe they never liked the pairing in the first place or they think it adds an interesting twist to the story. They could start exploring new relationships for both Sasuke and Sakura in their own fan - created stories.
If Naruto was an Ajin in a fanfiction, the characters in Naruto would have a mix of reactions. Hinata would be concerned for Naruto's well - being. She might be a bit scared at first because of his new and strange abilities, but still stand by him. The villagers, who have had a rocky relationship with Naruto in the past, might be afraid of him all over again. They could see his Ajin powers as a threat. On the other hand, Naruto's close friends like Shikamaru would try to understand what's going on and help Naruto control his powers if they can.
Sakura might be initially shocked and a bit scared of Robocop's robotic appearance. But once she realizes he's on their side, she would be interested in his technology and might even try to learn from it to improve her medical ninjutsu tools. Naruto, on the other hand, would be super excited. He'd probably want to immediately be friends with Robocop and would be eager to see what kind of cool moves he can do. Kakashi would be more cautious, observing Robocop carefully to assess his capabilities and motives.
Naruto would be thrilled. He loves being the center of attention and seeing all these stories about him would make him feel even more important. He'd probably want to meet the writers and tell them how cool he thinks their ideas are.
Some characters might be shocked. For example, Naruto himself would probably be really excited to see how his world is imagined in the future. He'd be happy to see that his story has inspired so many different ideas. Sasuke, on the other hand, might be a bit more skeptical. He'd analyze the fanfiction carefully, looking for any inaccuracies or misinterpretations of his character or the ninja world's values.
Some might be amused. Naruto characters have their own set of stories and adventures, and seeing the different and often wild ideas in RWBY fanfiction could be a source of entertainment for them.
They could have a range of reactions. Naruto would likely be excited and eager to see new stories about his world. He loves adventures and would be interested in seeing different takes on his life.
Chiron would be concerned. He knows how important their relationship has been for the stability of the camp and for their own growth as demigods. He would likely try to mediate and help them work through their issues, if possible. If not, he would worry about how it will impact their future quests and the overall well - being of the camp and its inhabitants.