"How on earth," Merlin grunted through tightly clenched teeth, for Gwaine's ears only, "did Gaius manage to get the damn thing up here in the first place?" What he'd really like to ask, of course, was why Gaius felt the need to ask him to fetch the extremely-important-and-extremely-rare-and-extremely-vital-so-don't-you-dare-drop-it-Merlin-or-you'll-never-see-anything-except-the-leech-tank-ever-again potion from the top of what had to be the tallest cupboard in the entire castle with Gwaine right there, slouched comfortably in a chair at one of the cluttered tables because if he'd only held off until Gwaine wasn't there, Merlin wouldn't be leaning up a little farther on his toes and fumbling blindly up over his head atop the cabinet, his searching fingers finding only dusty wood and empty air—he wouldn't have even needed words, just a flash of his eyes and a flick of his fingers but your magic isn't for tricks Merlin, and it's certainly not to save you from work, that's the absolute last thing you need, something to make you even lazier—

"No idea." Gwaine gave a supremely unhelpful shrug, and slouched a little deeper in his chair. "Lassoed somebody, probably," he added, voice barely above a whisper.

In spite of himself, Merlin laughed. A quick glance over his shoulder at Gaius confirmed the old man was still deep in his book on-well, some plant or other. Even so, Merlin lowered his voice a little. "Then threatened to make their potions taste particularly awful unless they did." He turned back to his task, stretching his arm back as far as he could and scrabbling around a little, without real hope.

"And all so he could drag some poor fool into getting it down for him again, a hundred years later," Gwaine finished off in a whisper, a smile audible in his voice—a long, screeching scrape of wood on stone behind Merlin let him know Gwaine had risen from his seat. "I'd better get back," the knight continued, slightly louder as he drew up behind Merlin, and away from Gaius. "Princess won't be pleased if I don't turn up."

"Let him know where I am, will you?" Merlin tossed a glance behind him at Gwaine. "Pretty sure I'll be here a bit." He jerked his head at the cabinet.

"Yeah, 'course," Gwaine grinned crookedly. "Good luck with that," he tacked on, eyeing the cupboard apprehensively. "Think you're going to need it."

Merlin laughed—and his fingers closed around cold and dusty glass.

"I've got it!"

The bottle, or perhaps the potion inside it, was far heavier than he had imagined, and he had to latch on with both hands just to drag it gingerly to the edge of the cupboard. It was full right to the brim with something green, thick and globby-looking—he didn't envy the poor man who needed it.

"Nice one!" Gwaine jabbed him enthusiastically in the ribs in congratulations—and his fingers moved so quickly and lightly and unexpectedly that Merlin couldn't stop himself and a laugh—all right, fine, no, it wasn't a laugh, not really, it was actually a kind of—well, a kind of squeal, to tell the truth—yes, fine, all right, there was no kind of about it, it was a squeal—and it erupted sharply and, yes, fine, a little bit shrilly as well, from his lips—and absolutely the only thing he could say for it was at least it didn't last very long—but no, wait, that wasn't a good thing, no, that wasn't a good thing at all and now silence pressed so heavily on his ears it was nearly a physical thing and Gwaine's eyebrows had almost disappeared behind his usual curtain of dark, shaggy hair and his grin didn't look nearly so friendly anymore—

"Gwaine," Merlin hissed, "don't—" He couldn't say he hadn't expected it this time, but a yelp of laughter still escaped, and he jerked a little, when Gwaine's fingers found his ribs again—by some miracle he kept both hands latched firmly onto the potion bottle—oh, gods, the potion bottle. All right, it was official. He was fucked. "Gwaine," half-warning, half-pleading, "don't, honestly, Gaius will kill me—"

Gwaine pounced. Strong, skillful hands skittered lightly up and down unguarded sides—a loud shout of laughter ripped its way out of Merlin's mouth, and he nearly crumpled to the floor, probably would have if not for the potion, because Gaius would kill him if he spilled the potion and between Gwaine's teasing and Gaius' eyebrow, he knew which he'd take—at least until quick, nimble fingers worked their way over to his stomach.

"No, no, no, no," he wriggled a little, "not there—!"

Gwaine paused. "Sorry, mate," he didn't sound sorry at all, "but I'm not the sort who wastes opportunities, you know?"

"I'll—I'll make sure your potions taste particularly awful!" Merlin shouted desperately. "I'll make sure your—your food is always cold on the patrols! And I'll talk Arthur into giving you all the night shifts and you'll never see the inside of another tavern—no, no, Gwaine—!"

Gwaine dug his fingers into Merlin's stomach.

Merlin collapsed into laughter, moving about as much as he dared, his arms shaking as he struggled to keep them up—the bottle tottered dangerously above his head—

"Sir Gwaine," Gaius calmly flipped his page, "kindly see to it that the potion doesn't fall, thank you," he turned back to his book. "Very difficult to make."

"—What—? Gaius—!"

Notes: I realized the other day that I've never written a friendship fic between Merlin and Gwaine, so I just sat down and whipped out the first thing that came to mind. It definitely got a lot sillier than I intended. Gaius is the Resigned Tired Dad who doesn't care what his kids are doing so long as they're not fucking shit up.