Another possibility is that Merlin would be deeply hurt. He might retreat into himself, his feelings of loyalty and friendship towards Arthur suddenly in question. He could become more withdrawn and less eager to help Arthur, which would then create more tension in their relationship as Arthur realizes the impact of his words.
He might also get angry. Merlin has his own pride and after all he has done for Arthur, being insulted like this would make him furious. He could start yelling back at Arthur, listing all the times he has saved Arthur's life or the kingdom.
One possible reason could be a misunderstanding. Maybe Merlin did something that Arthur misinterpreted as betrayal or dishonesty. For example, if Merlin was secretly helping an enemy for a greater good that Arthur wasn't aware of at the time.
A fanfiction that stands out is 'Arthur and Merlin: A Different Path'. This one takes a different turn from the original storyline. It imagines a world where Arthur discovers Merlin's magic much earlier. This changes the whole dynamic between them, and they face different challenges together. There is also 'The Adventures of Merlin and Arthur in the Enchanted Forest'. It's full of exciting quests and the development of their friendship.
Merlin could be heartbroken. He might retreat into himself and become more withdrawn. After all, he has a deep bond with Arthur, and this sudden break - up would be a huge shock.
Merlin would be very worried. He would probably stay by Arthur's side day and night, using his magic secretly to try and heal him. He might also search for rare herbs or magical items that could cure Arthur.
Arthur might be initially shocked and confused. He's used to Merlin being in control. But then he might find it quite hilarious and start teasing Merlin about it.
One great fanfiction is 'The Once and Future King's Heart'. It beautifully delves into the deep bond between Merlin and Arthur. It shows how their relationship evolves over time, with Merlin's magic playing an important role in protecting Arthur while also creating some interesting conflicts.
One great 'Arthur Pendragon Merlin fanfic' is 'The Once and Future King' -esque story where Merlin's magic is a key factor in Arthur uniting the kingdoms. It shows their deep bond and how Merlin uses his powers to protect Arthur in a very creative way.
Merlin would likely be seen as a bit of an enigma at Hogwarts. His magic is different from the norm, so he might be a bit of an outsider at first. But his kind heart and loyalty would soon win over his classmates. Arthur would be the brave and headstrong character, perhaps a bit like a Gryffindor version of his usual self. He'd be eager to learn about combat magic and would probably be a natural leader in group projects or Quidditch teams.
Merlin might be initially shocked and heartbroken. He has been so close to Arthur, and this sudden forgetfulness would be a huge blow to him.
He might be initially startled. Arthur is used to a certain propriety in the court, so having Merlin suddenly on his lap would catch him off - guard. But then, depending on their relationship at that point, he could either laugh it off if they are in a very friendly stage or he might be a bit flustered and ask Merlin to get up if there are other people around.