"You are not," Arthur says, very reasonably, "one thousand years old."

"Oh, no," Merlin says, like that would be absolutely ridiculous, "oh, no, of course not, Sire, no, I'm certainly older than that."

"Come off it, Merlin," Arthur says, still very reasonably, "you're full of horse dung. You're younger than me by two years."

"Am I?" Merlin arches a brow.

"Yes!" Except there's an icy sort of uncertainty in the pit of Arthur's stomach now—all that Merlin is actually magic itself and Merlin is the son of the earth and the sea and the sky and Merlin might really be some weird sort of god, all the things he isn't really ready to face just yet, come rushing back to meet him in a great, surging wave— "You—you told me so yourself! The first week we met!"

"And you remembered," Merlin puts his hand to his heart. "I'm touched, Arthur."

"Shut up, Merlin," Arthur says. "You're younger than me. I know it."

"Oh," Merlin says, and blinks up at Arthur with those big, blue, deceptively innocent eyes of his, "like how you knew I was a sorcerer?"

"Shut up, Merlin!" Arthur does not bleat. Absolutely not. There is no bleating here. Kings do not bleat. "You're—you're joking." Oh, God, please let him be joking. "And it's a very bad joke, you don't even look old!"

"Don't know if you've noticed," Merlin wrinkles his nose, "but it's really not very convenient to have a three-thousand-year-old body when you've got a royal prat to run 'round saving all the time."

Oh, God, Arthur doesn't think he's joking. "But," he croaks, weakly, dragging up the words from the back of his throat, his last and extremely desperate attempt to stitch the fraying threads of reality back together again, "but your—your mother's young—?"

"Oh," Merlin says, cheerfully, "you don't think that's really her true form, either, do you?"

Oh, God. Arthur's already getting his once-a-day Merlin headache, and it's not even midday. He collapses, with a little thump, on the end of his bed. "You're joking." Because his idiot servant is not three thousand years old. He's just—he's just not. Because Arthur says so. That's why.

"I assure you, Sire," Merlin says, "I am not."

Arthur stares at Merlin. Because he's joking, he's got to be joking, and God knows Merlin can't ever keep a straight face for more than a minute when he's joking.

Merlin stares right back at Arthur. After the first twenty seconds or so, one corner of his mouth starts to twitch, and then to quiver, and then he throws his head back, and lets out the loudest, brightest laugh Arthur has ever heard. "Oh, God, you actually—! I actually had you?!"

"No!" Arthur says, reflexively. "No, of course not! Don't be an idiot, Merlin!"

But it doesn't do so much as an ounce of good, because Merlin doesn't believe him, and just keeps on giggling to himself, like an absolute maiden, one hand pressed tight to his mouth to hide his stupid, enormous, cheeky grin. Stupid little sneak. Maybe, this whole time, he's been the bad influence on Gwaine, rather than the other way 'round.

"Oh, God, Arthur," Merlin says, words warped by his own breathless laughter, "you are just too easy!"

All right, that's it, the idiot is just asking for it at this point.

Arthur yanks Merlin down by the tattered edge of his stupid red scarf, pulls him in a headlock maybe a little tighter than it really needs to be, and scrubs his knuckles mercilessly over the tangled mop of dark hair.

Merlin gives a squealing sort of yelp that sounds absolutely nothing like an ageless, all-powerful warlock, and absolutely everything like Merlin. "No! No, no, no, Arthur, stop! Stop! I take it back! I give! I give! Arthur—!"

Notes: more Merlin fucking with Arthur because he can