Arthur stood before his throne room, which was filled with people; Merlin, as always, stood just behind him. The king had gathered the knights of the round table, the council, and a fair number of servants. "I have one last announcement to make today. I have recently been issued a challenge of honor." The crowd collectively gasped, silencing themselves. Arthur had opened his speech with a straight face, pretending to be serious, but now the makings of a smile tugged at his lips. "The challenge was made by my manservant, Merlin, as most of you know, and while I am under no obligation to accept the challenge, he champions for better pay for the serving staff of the castle, so I have decided to humor him."
Arthur paused, waiting to see the reactions of the group of his most trusted people… and the other people in the room. There were a few scattered snickers and amused smiles, especially among the knights, but mostly the group appeared to be indifferent to the news, now knowing it was not an official knight's challenge and thus didn't affect the safety of the kingdom or the honor of their king.
"Three days from now, he and I will trade places. I will work as a servant for a full day, during the first day of my sister's arrival in Camelot and the subsequent feast, and he will perform all of my regular duties as King."
This part of the announcement got some objections. "Sire, surely he can't—" One of the council members argued above the murmurs of the crowd.
Arthur raised his hand to quiet the mild uproar, cutting off the objections. "Merlin has been in my employ for almost a decade and for all four years that I have been king, he knows how I run my kingdom. I am entrusting him with this knowing he is capable of doing it. And of course he will not be with the full power that I wield, either Queen Guinevere or Sir Leon will be with him at all times and will regulate his decisions, as they do with my own decisions." At the word regulate, Arthur smirked and gave Merlin a sideways glance. Merlin give his biggest grin to the crowd; his heart was ready to burst at the sentence about Arthur's trust in him.
"During this time, all people should treat him as they treat me and treat me as they do him. Specifically, he should be called sire and bowed to while my title should be dropped, and the servants should not be afraid to ask me to do anything they would normally ask his help for."
A few people still eyed their king skeptically, but most began to nod their heads as Arthur continued to explain their plan. "At the end of that day, Sir Leon and one of the head servants will report to Queen Guinevere and will help determine who won the challenge and ultimately whether or not I will be raising the wages of the serving staff."
At that statement Arthur dismissed the people in the room. He turned to look at his servant, who was failing to bite back a large grin. Arthur smirked, he certainly wouldn't make it easy for Merlin, he'd give his friend a proper challenge.
Arthur and Merlin spent the next few days in excited anticipation. Arthur made snide comments about Merlin's inability to hold a sword properly and how he wouldn't be able to train the knights if he couldn't even hold a sword. Merlin snarked back that Arthur would finally have to do real work. The two were throwing thinly veiled insults and trash-talk at one another constantly. The knights encouraged their competitive spirit, secretly placing bets on the official winner of the challenge, while the queen stopped to reprimand them for their words more than once.
Merlin had also spent that time discussing the challenge with every servant in the castle. They all wanted him to win, not only for the increase in their salary, but for the recognition that a servant's work was hard and shouldn't be taken for granted.
Merlin assured them that he was fully prepared to complete this challenge and encouraged them not to hesitate in asking their king for help when the time came. He knew it wouldn't be easy for them to go against everything they'd ever learned and not stumble through formalities in the presence of royalty, even if he was acting as a servant.
The night before Merlin led Arthur to his room, reminding him that Gaius would wake him in the morning when he was inevitably late. Then the servant headed to the king's chambers.
Arthur logically knew he would have to get up earlier than he normally did so he wasted no time in changing into nightclothes he had brought with him from his own room and falling into Merlin's bed.
The only thing he bothered to do before retiring for the night was to put his nice, kingly, clothing into Merlin's wardrobe. He'd have to remember to retrieve them after this whole thing had finished and he had beaten Merlin at his own game.
Merlin entered Arthur's room and closed the door, lighting a candle with magic so he could see. Merlin had already changed out of his tunic and neckerchief because unlike the king, he didn't have any particular issue with walking through the castle in his nightclothes. It wasn't like he had a reputation to maintain; everyone already thought him to be at least a little weird.
Like Arthur, he went directly to bed, curling up in the softness of Arthur's pillows and mattress. He had napped on them before—allegedly—but being able to sleep an entire night in the luxury sheets would be wonderful and Merlin didn't want to waste any of that time wandering around doing other things.
He extinguished the candle without leaving the bed and before long he was softly snoring.