A/N: This was written for the Holiday Armadillo Fic Exchange in the mark_n_callie community on LJ, those of you that know of it. It's holiday-themed Mark/Callie three-party. Expect fluff, angst, and non-graphic sex. There ya go. Happy Holidays :)

Disclaimer: I am certainly no way affiliated with Shonda or ABC. If only, if only.

Lines

Part One

Mark and Callie were fuck buddies. Simply put, that was the way things were. They were best friends still, who relied on each other for everything. And now, once again, that everything included good sex. But that was all it was: sex. They were fuck buddies. Friends with benefits, like they had been before.

Callie and Arizona had broken up in late October, just before a Halloween party they'd all been invited to at Joe's. It was over something terribly stupid – Callie hadn't wanted to match Arizona's Halloween costume because she'd already promised to be the leather-clad Catwoman to Mark's Batman. It was the last straw for Arizona, it seemed. Callie spent the length of the party drinking her sorrows, overindulging to the extreme, and then going home and spending the night and early morning sobbing into Mark's shoulder.

The next morning, seeing Mark had spent the night with Callie and not in his own bed with his girlfriend, Lexie broke up with Mark. No excuse worked. It would seem she was fed up, too.

The pair of best friends spent the day drinking even more and ended up in bed together. It was familiar. It was natural. From that day onward, they resumed their position as fuck buddies.

It was just sex, they both knew. Just like it had been before. Nothing but sex with no strings. They were best friends and continued to spend their days together, but now they spent the large majority of their nights together, as well. Callie, however, was always very careful to make sure that she crossed the hall back to her own place at the end of the night (or make sure Mark went back to his). She never stayed the night at Mark's, and she never let him stay the night at hers. Staying the night, Callie had decided, would be ruining the distinction between friends and lovers. Lovers spent the night. They curled up together with a sense of intimacy. It was what lovers did, not friends with benefits. It was about the benefits, not the aftermath. Physical, not emotional. There were certain rules that had to be followed when fucking your best friend, and Callie knew she could not slip up and let those lines blur. She'd let herself be hurt too many times before.

If she let herself fall for her best friend, it would be much worse.

* * *

"Come shopping with me," Callie requested with a smile. She had just approached Mark in the hospital's hallway.

"Shopping, Torres? Really?" Mark asked dryly.

"I need Christmas stuff. You can buy some, too!"

"I don't need Christmas stuff," Mark said. "I live alone. I'm not decorating."

"Well…we'll do Christmas at my place. You can help me decorate."

"Callie," Mark drawled, "that is boring."

"So…we'll drink while we do it. Just go shopping with me, at least."

Mark grudgingly gave in. "Fine. Is your shift over?"

"Will be in ten minutes," Callie grinned cheekily.

"I'll meet you at your car."

Thirty minutes later, Mark and Callie were inside the store. They grabbed ornaments, lights, and something Callie absolutely refused to show Mark, checking it out at a separate register. Mark insisted on buying eggnog.

"Look at you getting into the holiday spirit," Callie laughed.

"So I like eggnog? It's only available this time of year."

"Sure, Sloan," Callie teased. "Sure."

Mark rolled his eyes.

Callie glanced out the window and gasped. "Mark, it's snowing!"

"Your point?" he asked, seemingly bored.

"I love snow," Callie beamed.

Mark chuckled. "It's just snow, Torres. It's what happens during the winter time."

"I love snow," Callie repeated. "I didn't snow much when I was growing up, and when it did, it never stuck. It melted the second it hit the Miami pavement. Snow is exciting for me. You're from New York, so it's nothing for you, but it's a big deal to me. I love snow."

"Well then, I'm glad it's snowing," Mark decided.

The pair headed outside with their bags after checking out, and they lugged them into the trunk of the car. Callie stuffed her secret purchase into her purse quickly, but Mark saw a brief flash of red. What the hell was she hiding?

Mark headed towards the passenger door, planning on getting inside the car, but Callie didn't seem to be following. He furrowed his brows, confused as to what she was doing. He turned around and received a snowball to his leather jacket-clad chest. He gaped at her and grinned.

"Oh," Mark spoke, "You are in for it."

He was quick to make his own snowball and throw it at Callie. Snowball after snowball were thrown, and snow covered Callie's black hair. Snowballs slid off of Mark's jacket, leaving big wet streaks. Callie started shivering, her gloveless hands freezing and red from the snow.

"Come on, Torres, you're freezing." Mark flashed her a roguish smile.

Callie wiped her hands and rubbed them together, trying to warm them up.

On the drive home, Mark asked from his spot next to her, "So what's the secret item you bought?"

"I'm not telling," Callie spoke coyly. "It's a surprise."

"Is it my Christmas present?"

Callie laughed. "Let's just say we're celebrating early."

Mark quirked a brow. "Are we now?" He was getting an idea of exactly what type of item she had purchased, and he liked it. He liked it a lot.

"Mm," Callie hummed, "We are."

When they got back to Callie's place, Yang was nowhere to be found. She must be at Owen's, Callie decided, figuring she was staying the night. She was pleased – they often stayed at Mark's because he lived alone. They didn't have to be polite about the noise and keep it down. Callie grinned.

"Nice tree," Mark smirked, gesturing to the obviously fake tree on the other side of the room.

"Shut it, Sloan. It's what I already had, and I wasn't about to go out and buy a tree that would probably die in a few days because I'm never home to water it."

"I'm not judging. I don't even have a tree. Now where's my present?"

Callie smiled seductively and led him to her bedroom. "Wait here."

Mark beamed, looking about as happy as a young child on Christmas morning, eyes full of the presents under the tree. He was getting a gift, after all. Several minutes later, Callie exited the bathroom, and Mark's jaw dropped.

Callie was wearing Christmas "" themed lingerie. The bra and panties were red velvet with white fuzzy lining. To top off the ensemble, she was wearing a Santa hat and red pumps.

She smiled suggestively. "In the holiday spirit yet?"

Mark whipped off his shirt, licked his lips, and said, "Hell yeah."

Callie giggled as he pulled her toward him. Her hat fell off, and Mark ran a hand through her messy curls. He'd always loved her hair. Whenever it was up in a ponytail, he had a tendency to pull the hair band out and steal it so that she could not put it back up until she managed to find another one.

Mark kissed her hard on the lips and lowered her to the bed. His fingers felt the soft material of the bra, and he let out a small sigh. "I like my gift, Torres. I really like my gift. It will be hard to outdo on Christmas."

Callie laughed as he deftly removed her bra and panties, then quickly ridded himself of his own remaining clothing.

Sex with Mark, Callie noted as he sunk into her, was always fantastic. Whether rough and bruising or slow and building, sex with Mark was always very good.

This time was no exception.

It was passionate and hard and great as always. Callie bit her lip until it bled when we brought her to her climax the second time.

The two lay spent and sweaty on the bed, breathing heavy.

Mark turned and grinned lazily at Callie. "Happy holidays, indeed, Torres. I'm definitely in the spirit now."

Callie smiled back halfheartedly.

They lay there for a few more minutes, sticky and tired, until Mark rolled out of bed and redressed.

"I'll see you tomorrow," he said and kissed her quickly on the lips before exiting to his place across the hall.

Callie blinked away the wetness she felt pooling in her eyes. He always left at the end of the night. She did the same. It was the unspoken rule. No boundaries could be crossed.

No lines could be blurred, Callie reminded herself for the umpteenth time.

But there was no stopping it. Callie Torres was actually falling for Mark Sloan.

"Shit," she whispered to herself, trying to wipe a stray tear from her face.

She was screwed.

--

End of Part One. The next one should be up soon. Reviews are appreciated, I like to know I have readers. :)