A loud rap at the door woke Arthur up from his sleep.

"Go away," the young man grumbled, covering his ears.

"Come on, Arthur," Gaius's voice said impatiently. "You know Merlin hates it when you're late."

Arthur froze, trying to absorb what Gaius just said. Why was Gaius even outside his room, anyway? He sat up, confused. "What do you mean, Merlin hates it when I'm late?"

"Well, you are his manservant," Gaius replied. "Get up!"

Arthur was well and truely puzzled now. He rubbed his head, glancing around his room. Or... Merlin's room.

"Okay, very funny!" Arthur shouted, getting out of his bed - Merlin's bed, he realised. Of course, his own sheets weren't as irritating. "Merlin's put you up to this, hasn't he?"

No reply came, so Arthur began to walk towards the door. Merlin's room was as messy as ever, with clothes, books and armour strewn across the floor, and Arthur had to walk through carefully in order not to tread on anything.

He flung open the door, stamping downstairs.

"Ah, you're finally up," Gaius grinned at him. "You forgot to get dressed, though."

Arthur glanced down at himself; he was dressed in a long nightshirt and baggy trousers.

"Okay, come on," Arthur scowled, impatience rising in him. "Merlin's put you up to this, hasn't he?"

"Merlin?" Gaius echoed, looking confused. "He hasn't asked me to do anything."

"Don't give me that." Arthur pushed past him and opened the door. "I bet that he's in my room, while I was in his."

"But... but, Arthur, you were just in your room."

Arthur groaned. "Oh, forget it." He strode out the door, slamming it behind him.

Merlin's earned himself another day in the stocks for this stupid prank, Arthur thought to himself as he walked to his room. honestly, of all the things he could have done...

Arthur stopped, then took a few steps back. A window was set in the wall of the corridor, and Arthur could just about make out his reflection. He stared in shock.

The muscles he'd gained from endless battles and training were gone, leaving him with a scrawnier figure. His hair looked identical to Merlin's, except that it was still blond, and his eyes had become darker. Arthur glanced down at his hands - they were skinnier than he remembered, and with slightly paler skin.

"MERLINNN!!!"

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

A few shafts of sunlight fell across Merlin's face, making him blink twice before rolling over. He felt warm and comfortable, lying here, and his sheets felt softer than they ever had. He snuggled down, absentmindedly pushing back a few strands of hair from his eyes.

Hang on...

Merlin stared at his hand, frowning. Maybe it was the sunlight, but his hand looked darker, and more muscular. He flexed his knuckles, watching as they responded.

"Hmmm..." He slowly sat up, staring down at himself. He was wearing a nightshirt, but Merlin couldn't help noticing that his chest also seemed more muscular than usual.

Suddenly his door flew open, and Arthur ran in. "Merlin!" he yelped, skidding to a halt. "What did you do?"

Merlin stared at Arthur for a second, then burst out laughing. "Sorry!" he apologised quickly, still giggling. "You just look..."

"Well, have you seen yourself?" Arthur retorted, putting his hands on his hips.

Merlin stopped laughing. "What do you mean?"

Arthur sat down on the end of the bed. "See for yourself," he gestured towards a mirror that stood in the corner.

Merlin glanced around the room, noticing for the first time that he was in Arthur's room/ Slowly, he got out of bed and stood in front of the mirror. His jaw dropped.

Merlin's black hair was longer than before, shaped around his face like Arthur's usually did. His eyes were lighter blue, and he realised that he really did now have a more muscular form. He twisted from one side to the other, his eyes wide.

"So now you understand," Arthur muttered, crossing his arms over his chest. The anger he'd first had was gone, and now he seemed more curious. "You honestly didn't do this?"

Merlin slumped down on the bed beside Arthur. He rested his head on his hands."I... I don't understand..."

"Maybe Gaius was telling the truth, then," Arthur wondered. "Saying that I was your servant..." His eyes widened suddenly. "Merlin!"

Merlin was staring at him, open-mouthed.

"Am I meant to be...?" Both of them said at the same time.

Merlin jumped to his feet, staring at his reflection again. "So, I'm the Prince?"

"Oh, I hope not," Arthur groaned. "That would mean that I'm a servant."

Merlin ruffled his hair. Instead of looking weird like usual, it fell into a handsome style. "Ummm... Arthur?" he said hesitantly, turning to his friend. "Yesterday, I was annoyed about you putting me in the stocks, and I kinda wished that you could understand me a bit more..."

Arthur stood up next to Merlin, and they gazed at their altered selves in the mirror. "Well," Arthur admitted, averting his eyes. "I did the same."

Merlin glanced at him, surprised.

Arthur moved over to his window, remembering how he'd stood here last night. Dawn had broken now, and the same people who had cleared away their stalls last night were setting them up. "But how do we know for sure? You know, if our lives have been switched."

Merlin frowned, thinking hard. Finally, he walked over to the door. Of all the people who could have been walking past, it was Gwen, carrying Morgana's breakfast tray.

"Gwen!" Merlin called to her.

She turned, a look of shock on her face. "Sire?" she said nervously.

That 'Sire' told Merlin most of what he needed to know. Just to make sure... "Gwen, who am I?"

"Why, you are Prince Merlin of Camelot," Gwen replied cautiously.

Merlin raised his eyebrows. "And... my manservant is...?"

Gwen blushed slightly, averting her eyes. Merlin was used to that look; she did it almost everytime he said her name. "Arthur."

"Thanks, Gwen." Merlin closed the door, turning back to Arthur. "Well, that clears things up," he said quietly.

Arthur nodded, running his hand through his hair. Merlin noted with some brief satsifaction that made his hair look messy rather than stylish. "Now what?"

"Errr...." Merlin realised that they were both still in their nightwear. "We get dressed?"

Arthur glanced down at himself, touching the fabric of his shirt. "What, in each other's clothes?"

"Technically we were never ourselves," Merlin corrected him. "It's like it's always been this way."

"But it hasn't!" Arthur argued.

"I know," Merlin sighed. "But maybe we should just go along with it for now."