Set after series 2, Merlin and Arthur are more open about their friendship with each other, but only with themselves, each other, Gwen and Gaius. Morgana is not in Camelot.
It was winter in Camelot and it was freezing. Arthur was getting over a cold, and had been informed by his father that there was to be no training his knights, no hunting and no, well, anything outside. He was confined to the castle. And he hated it. For the third day in a row Merlin and Arthur were lazing about in Arthur's room, Arthur because, well, it was his room and Merlin because Arthur had decided he needed Merlin as a friend more than a servant at the moment and had passed all his duties to another boy. Temporarily, mind you.
"I hate my father and I'm bored." Arthur announced suddenly, and turned back around from the window to face Merlin. He stopped short at the sight of the sudden Cheshire cat grin on the manservant's face.
"What?" Arthur asked with a mixture of curiosity and suspicion.
"I know just what to do. To make you feel better".
Arthur didn't ask. "let's go".
20 minutes later saw Merlin and Arthur in the royal stables with a bucket of white paint. Right next to Uther's horse.
"Merlin, what exactly are we going to do?" Arthur asked, still not cottoning on to the plan.
"Arthur, have you ever seen or heard of a zebra?"
"Yeah?" he replied baffled.
"What do they look like?" Merlin asked, still with a smile on his face.
"They look like small horses except that they have black and wh-". Arthur stopped and looked from Uther's black horse to Merlin's grin and then down to the white paint bucket in his manservant's hands.
"Oh...I like it" Arthurs grin growing to match Merlins. "Let's get started..."
Two hours, a paint fight and a zebra-d horse later...
"What on earth is going on here!" Uther yelled at the sight of his poor horse. Merlin and Arthur snickered quietly from their hiding place, watching Uther's temper boil.
Arthur hadn't had this much fun in ages. "Thanks Merlin." He whispered sincerely.
"No problem" Merlin whispered back, not taking his eyes of Uther. "I'm getting as much enjoyment out of watching Uther's reaction as you are."
After a few more seconds of amused silence from the boys, Merlin sighs and whispers: "We better get going. We are covered in white paint and if Uther finds us we'll be in so much trouble. Especially me, and I don't want to end up in the stocks again. Plus it'll be a nightmare for me to get the paint out of our clothes if it dries any more. Not that it's going to be easy anyway."
Arthur opened his mouth, but Merlin beat him to it. "We can't get anyone else to do it. They'll put two and two together-"
"-and come up with nine", Arthur interjected with a snort.
"Just because they are servants doesn't mean they are stupid!" Merlin snapped, suddenly irritated.
Arthur winced. Nice move jerk, he thought to himself.
"Sorry, I forgot you're technically a servant, since I've always thought of you as my friend." Arthur paused, waiting for the whispered reply. He didn't have to wait long.
"S-OK, shouldn't have snapped at you. Sorry." Merlin replied, slightly sheepish.
Arthur smiled. "Doesn't matter. Let's head back to my room."