Characters could be either excited or offended. If the crossover fanfiction portrays them in a positive and interesting new light, they might be excited. But if it misrepresents them or makes them look bad, they could be offended. For example, if a heroic character is made into a villain in the fanfiction, they would not be happy about it.
Well, first of all, Natsu would probably be excited to see himself in all kinds of wild adventures in the fanfiction. He loves action and if the fanfic has him in some epic battles, he'd be all for it. Lucy might be a bit more critical. She'd look at how she's portrayed in terms of her intelligence and her relationships with the other guild members. Gray would likely be cool about it, but might get a bit annoyed if the fanfic made him seem too cold or too goofy. And Erza would be very strict in her assessment. If the fanfic doesn't adhere to the values of the guild she holds so dear, she might not be too happy about it.
Natsu would probably be really excited at first. He loves dragons and having a dragon king around would be like a dream come true for him. He'd probably want to immediately challenge Tiamat to a fight to test his strength. Erza, on the other hand, would be more cautious. She'd be on guard, making sure that Tiamat doesn't pose a threat to the guild. Gray might be a bit indifferent at first, but as he sees how Tiamat could be useful in battles, he'd start to warm up to the idea.
The guild as a whole would likely mobilize. Erza would start formulating a strategic plan. She'd consider the strengths and weaknesses of Acnologia and figure out the best way to approach the situation. Gray would also be ready to fight, using his ice - make magic to support the rescue mission. They would all be united in their determination to get Lucy back safely.
The Fairy Tail guild would probably be very curious about Naruto at first. They might be amazed by his strange abilities like running up walls and creating clones. Some members, like Lucy, would likely be a bit cautious, but also intrigued. Natsu would probably be eager to test his strength against Naruto right away.
Some bullies might mock BTS fanfic. They could make fun of the fans who write or read it, thinking it's just some silly obsession. They might not understand the creativity and passion that goes into creating these fanfics.
Some bullies might mock or make fun of spiderman fanfic. They could see it as something only 'nerds' are into and use it as another reason to pick on fans. For example, they might laugh at the outlandish plot ideas or the 'geeky' passion of the fans.
The guild would likely be shocked at first. They consider Natsu as one of their own, so his attack would be completely unexpected. Some members might try to talk him down, like Lucy. She has a close bond with Natsu and would probably try to reason with him.
Natsu would be heartbroken. Fairy Tail is like his family. He'd probably go on a solo journey to clear his name and prove his loyalty. Erza would be stoic but deeply hurt. She'd start an investigation within the guild, using her influence and intelligence to uncover the truth. She might also isolate herself a bit while she figures things out.
The members of Fairy Tail would likely be shocked and angry. They would feel betrayed because Naruto had probably become a part of their family. Natsu, for instance, would be enraged and might immediately challenge Naruto to a fight. He's hot - tempered and wouldn't take kindly to someone he considered a friend turning against the guild.