"I rather think not." Arthur had limited experiences with the extent of magic's more obnoxious side, but he wasn't daft enough to miss the signs. Which meant either Merlin was enchanted, or he wasn't Merlin at all.
Neither of which boded well for either of them. Playing along wasn't so much an option as a given. Arthur folded his arms and said, "All right, not Merlin, what should I be calling you?"