This idea's been biting me in the ass for a long time, so I sat down and wrote it in about fifteen minutes tonight. Sorry for the sloppiness.

Disclaimer: Grey's Anatomy is the property of Shonda Rhimes and ABC. This writing is for entertainment purposes only and is not for profit.
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It was a boring afternoon at Seattle Grace Hospital, and Derek didn't have a surgery. Meredith did. Everyone did. Or, at least, everyone said they did, perhaps just to make him feel even more bored.

He was sitting completely alone in the gallery of OR 2, glancing up every so often from the paperwork in his lap to glance at Bailey and the bowel she was elbows-deep in. Then it was right back to writing repetitive phrases in shorthand, initialing, and making his quick, loopy signature. Time trickled by like water from a dripping faucet. He cracked his neck. He yawned. He rubbed his eyes when the text on the paper began to swim.

It was a boring, boring afternoon.

When he was on the penultimate page of the packet, the door opened. Mark stepped through, and Derek cringed inwardly when he saw his best friend's face. His blue eyes were huge and shining, lips twisted into an uncontrollable sort of goofy grin. This could be no good. He really didn't want to know. Luckily, Mark just allowed his smile to become more lopsided when he saw Derek, who raised his eyebrows in silent greeting, before taking a seat in the row of plastic chairs behind him. Derek went back to scribbling "DS" on the paper in several different places.

Sloan didn't allow the ignoring to go on for much longer, though. He cleared his throat, and after Derek didn't acknowledge it, he did it again, much louder. Derek closed his eyes and sighed. Obviously Mark wanted to tell him something. He was about as subtle as an explosion.

"Hi, Mark," Derek said dryly, turning around, raising an eyebrow.

"Derek," Mark replied, the silly smile still plastered to his face, eyes crazy. Derek was, quite literally, afraid.

"What's going on, Mark?"

"Oh, nothing," he said nonchalantly, placing his hands on the back of his head and leaning backward as far as he could. "It's just…Lexie." Derek winced. He knew this was coming.

"What about Lexie?" The reluctance in his voice surprised even him.

"She…" Mark lurched forward, almost causing Derek to topple over in fright, voice dropping to a hushed, excited whisper. "She plays the trombone."

Derek recoiled, face scrunching in confusion. That was it? Hardly the egregious, disgusting statement he had expected to come pouring out of Mark Sloan's mouth.

"Oh. Well, that's nice," Derek said, relieved. Something was telling him he already knew that – Meredith might have told him. There was something about apples and an Etch-A-Sketch attached to it. He must have been drinking.

Mark, on the other hand, didn't look satisfied. He deadpanned, staring at Derek so intensely it forced Derek to face him again.

"What, Mark?" he asked, trying to keep his annoyance from infiltrating his voice.

"Lexie plays the trombone," Mark repeated, widening his eyes and drawing out the final word to put more emphasis on it. Again, Derek was clueless.

"You know, sometimes I don't understand you. Do you mean to say that the fact that she plays the trombone is a bad thing? Like she's a band geek or something?" He clicked his tongue at his friend. "Because, you know, I played in the band. So did Bailey. And we're both pretty cool." It was a good point until an image of Lexie, Bailey, and himself jamming together on their respective instruments crept into his head. He had to shake his head until the very random scene dissolved.

Mark snorted out loud. "No, it's not that. I'm not calling Bailey a geek, I don't have a death wish. But Lexie is worlds cooler than you," he teased. "But that's not even it. You're not listening to me. I want you to look me in the eye right now, Derek Shepherd, and listen carefully when I say that Lexie Grey plays the trombone."

Derek gazed at him intently, and Mark made the disgusting mouth and hand gesture to accompany his words.

And, with that, renowned neurosurgeon Derek Shepherd fell out of his chair.