Well, the other characters' reactions would vary. For example, Mirajane would have a big smile on her face. She's always interested in the love lives of her guildmates. She might start planning a romantic scenario for Natsu and Erza right away. Elfman would be a bit uncomfortable, muttering something about men not being so clumsy. Lisanna would be excited and encourage Erza to give Natsu a chance. Cana would bet on whether they will end up together or not, and Gildarts might give Natsu some fatherly advice on how to handle the situation with Erza.
Sakura would probably be very surprised and might feel a bit of jealousy if she has some lingering feelings for Naruto. She could act cold towards Ino or Naruto for a while. Shikamaru, being Ino's friend, might tease her about it a lot, but also be a bit protective. Choji would likely be more concerned about how Ino feels and might offer her some snacks to cheer her up if she's flustered.
Sure. In such a fanfiction, it might occur during a celebration. Everyone is having a great time and Natsu, who is excited as always, jumps around and accidentally bumps into Erza. Their lips meet for a brief moment. Immediately, Natsu realizes what he has done and freezes. Erza is stunned. After a moment of silence, Erza might give Natsu a stern look, but deep down she's a bit flustered. Natsu then spends the rest of the day trying to avoid Erza out of embarrassment, while Erza is left thinking about that unexpected kiss.
Yes, there are likely some fanfictions out there with such a plot. You can try searching on popular fanfiction websites like Archive of Our Own or FanFiction.net.
Typically, you can expect a romantic or perhaps a very emotional scene. It might explore the relationship between Natsu and Erza in a new light, showing how they feel about each other.
The guild master would likely have a very fatherly or motherly reaction. They would ensure that Natsu and Lucy have all the resources they need. Mirajane would be overjoyed and would start planning all kinds of things for the baby. Elfman might see it as a sign of Natsu becoming a real man and offer to train the baby when it grows up. However, there could also be some characters who are jealous or feel left out. For example, someone who has a secret crush on either Natsu or Lucy might be a bit bitter at first but would eventually come around to support them.
The reactions would be mixed. Some of the younger members might be a bit in awe and look up to Natsu and Erza even more. However, there could be some concerns too. For example, some might worry that having a baby will make Natsu and Erza less focused on protecting the guild. But overall, the love and unity in Fairy Tail would likely lead to a positive atmosphere of support for the couple.
Well, there would probably be shock. Gray might make some sarcastic remarks at first. Happy would be very confused, not sure how to handle the situation. And Master Makarov would likely be concerned about how this would affect the guild dynamics and the two mages' future in the guild.
Sakura would be protective of Sarada. She would want to make sure that Boruto has good intentions. She might initially be a bit against the relationship but would come around once she sees how much they care for each other. Shikamaru, being the smart strategist, would see this as a potential distraction for both of them. He would try to give them advice on how to balance their relationship and their ninja duties.
Well, perhaps Erza was tricked into believing something false about Natsu. Maybe she was misled by some enemy who made it seem like Natsu was going to endanger the guild. So, in her sense of duty to protect the guild, she took actions that Natsu perceived as betrayal.
Perhaps in the fanfiction, Natsu meets Erza in a completely new setting, like a parallel universe where the Fairy Tail guild doesn't exist yet. They start off as strangers but quickly realize they have similar goals. Erza might initially be a bit distrustful of Natsu's wild ways, but as they face challenges together, such as a group of bandits attacking a village, they learn to trust and rely on each other.