Title: Where the Lines Overlap
Pairing: Callie/Arizona
Rating: NC-17
Summary: Arizona and Callie are best friends and roommates while going to college.
Disclaimer: I own nothing. I do not intend to profit in any way, shape or form by posting this story. It's for fun, nothing more, and nothing less. Please don't sue me.

A/N: I warn you now, Mallie sex inside. You have been warned. MALLIE SEX INSIDE. As I wrote this, I felt like I was crossing a line. LOL Arizona and Callie will eventually get together, I don't know how long it will take. I have no idea why I came up with this idea, but I wrote and my LJ person ( greys_ajunkie ) pushed me to publish it. I like comments, even comments where you yell at me for the MALLIE sex that takes place. Okay, yeah, this is awkward…

"Are you seriously going to go out with just Mark tonight?" Arizona Robbins sighed and she leaned back in her chair and pushed herself away from the desk in front of her. Her computer was making whirling noises in the background as it saved the monstrosity that was her latest paper for one of her classes. She still had a few hours to work on it and, being the perfectionist that she was, she wasn't going to let those hours go to waste, unlike her best friend and roommate Calliope Torres.

"Yes, I am. I need sex, woman. Mark is safe, he's my best friend and there are no strings attached when it comes to him. Plus, I have to admit, the man has skills." She shrugged slightly as she finished applying the last of her make-up at the mirror that was next to the door of their apartment.

The apartment was a cute studio space and they took it because it was close to the school and had plenty of room. The downfall was that they shared a closet and everything was in one place. Callie's bed was on the left side of the huge space and Arizona's was on the right, both against the far wall. They had their desks next to the beds, but they could look across the room and see each other when they were in bed. They would spend hours talking to each at night, so they liked the set up. The center of the room had a small couch and an entertainment center and the opposite side of the apartment was the kitchen. Callie's father paid the lease on it with no questions asked when she begged him to pay for a place off campus and Arizona paid for their food since she wasn't charged rent. It was a good deal for both of them. She and Arizona shared a dorm room for their first year, it was how they met, and they both hated the cramped quarters. Three years later they were still living together and were the best of friends.

Well, they were more than best friends. Arizona thought they were soul mates. She wouldn't deny that she was head over heels in love with her roommate and it killed her that Callie was a very adapt player when it came to games of the heart. She had just broken up with her sixth boyfriend about three months ago and she decided she was done with dating until she finished this year of school at least. They both had impressive marks, but Callie noticed hers were slipping, so she wanted to make sure she maintained her grade point average. That meant less worrying about making some man happy, which she was perfectly fine with her because she had Mark Sloan. Mark Sloan was Callie's best friend, and good friends with Arizona by proxy, but Arizona was insanely jealous of Mark. Mark and Callie were a couple for a while, but decided they were better off as friends with benefits, which is why giving up relationships was perfectly fine with Callie, at least, that's what Arizona rationalized. Basically, she could have her cake and eat it too.

Arizona wanted to eat her cake.

Arizona sighed at the thought and turned back to her computer. She should just concentrate on getting this done tonight and studying, because thinking of Callie and Mark partying together and then knowing he would be getting Callie's candy just made her feel like falling over and dying. A brutal, knife through the chest, crack open the thoracic cavity, rip out her heart, fling it to the ground and then dance a Mexican hat dance all over it. Thinking about Mark having sex with Callie should never be done while writing a paper for anatomy and physiology. A knock at the door pulled her attention away from her thoughts and she looked over her shoulder at Callie and felt all the air leave her lungs.

Callie was wearing her trademark leather jacket. She had a shiny purple shirt on which draped just below her breasts, making her mid-drift fully visible and the tightest pair of black skinny jeans that Arizona could have ever imagined her ass being in. She wore knee high leather boots which the pant legs were tucked into. Her hair was curled all around her face and her make up made her beautiful dark eyes pop. Arizona felt butterflies take flight in her belly and they took a direct flight down to her clit, which rapidly started tingling with desire as her eyes went from Callie's face down her body. She quickly licked her lips and brought her eyes up to Callie's, who winked at her knowingly.

Arizona couldn't stop the blush on her face and she quickly pouted at Callie moved toward the door.

"Don't wait up." Was all Callie said as she opened the door and grinned at Mark. He popped his head around Callie's body and waved to Arizona. "Hey Blondie, have fun studying!" He and Callie laughed and Arizona offered a stiff, "Ha. Ha." The two shut the door and the moment they were gone, Arizona flopped her arms on her desk, her head hitting them immediately after.

Mark opened the door to The G Spot, their favorite little bar and dance club and Callie walked inside behind him. They made their way to the bar and both ordered a shot of tequila and whatever beer was on tap. "You should've seen how cute she looked as we left. She was pouting and I just wanted to run back inside, but I just told her not to wait up." Callie sighed as she downed the shot which was placed in front of her and then grabbed Mark's shot too and quickly downed it. Mark sighed and ordered another shot as they both sat on a bar stool. "Did you even ask her if she wanted to come?"

Callie coughed and spit out the small amount of beer she had just pulled into her mouth. She felt the sizzle of beer at the back of her throat and the bottom of her nose and she coughed again as she slammed the beer mug on the bar. She turned to Mark, her eyes watery and red from almost convulsing on the amber liquid. He was laughing. Of course he was laughing and when he finally calmed down he raised his arms at her in surrender. "I meant did you ask her if she wanted to come out tonight… with us, you know?"

"No, I didn't." Callie managed to get out between coughs. "She was still working on that paper and I didn't really want to disturb her. And then I got distracted, because she's so cute when she's concentrating…" Callie sighed and lowered her shoulders slightly.

"Ugh, enough, you've got it bad. Why don't you just ask her out? It's not like we don't know she's a lesbian and I'm pretty sure she has the hots for you." Mark wiggled his eye brows suggestively and Callie swatted him on the arm.

"She does not. And she hasn't been interested in anyone since Julie and that was last year. I think she's just going to worry about school for now, which I'm going to try and do too. I'll just use you to get rid of my excess sexual energy." Callie drank in another gulp from the beer bottle.

"I love it when you use me for my body." Mark chuckled and licked his lips before drinking from his bottle also. He didn't have a hard time getting ladies, but having sex with Callie Torres was always a highlight to him. She was gorgeous and knew how to please him and there were no strings attached. She was the perfect friend and lover when she wasn't pining over her best friend. She was kind of sad and pathetic right now.

"Buy me another drink, Mark; I want to be plastered before we head back."

Mark did as he was told, but frowned and shook his head. "One more is all you get. You're a lousy lay when you're plastered."

Callie scoffed, "I am never a lousy lay."

Arizona was lying in bed, trying not to cry while thinking about her pathetic life. Being in love with your straight roommate was one thing, but knowing she was going at it with a guy right now was a complete other thing. She wished she hadn't finished her paper, because the best way to get her mind off of Callie was through schoolwork. There was no wonder why she had been top of her class since starting here. She heard a key in the lock and glanced at the clock. 'Hah, Mark must have not lasted very long if she's coming back already,' Arizona cheered to herself.

The door thrust opened and Arizona heard a soft giggle, followed by a grunt. It was a grunt from a man, a male person, something that did not belong in her apartment. She glanced toward the door, thankful for the darkness in the room, and saw Callie stumbling in backward with Mark attached to her. They were kissing, his lips were apart and his tongue was pressing into the two gorgeous red lips below them. Callie stumbled slightly and Mark's arms wrapped around her, pulling her body into his and she saw how she ground her hips into his as she pushed the door closed with her hand. He kicked it the rest of the way closed and when they heard a snap, they began dancing their way to Callie's bed.

She watched Mark's hands push Callie's jacket over her shoulders, while she leaned back to let it fall to the ground. Their kisses were becoming more insistent as Mark took his own jacket off, followed quickly by his shirt. Arizona glanced at his upper body and decided that, for a man, he was pretty attractive. Of course, his chest was missing her favorite part of the female body and Callie's were perfect. Her eyes fell back onto Callie's luscious curves and she pulled her bottom lip between her teeth as she felt a wave of arousal course through her body. How she wished she was Mark right now, her hands moving through Callie's raven black hair, her own lips pressed against Callie's.

"Shh, I don't want to wake her." Callie whispered when Mark grunted particularly loud. Arizona likened it to a caveman being set lose. Arizona watched as Mark's hand worked its way up Callie's side and over her breast. She watched as that hand squeezed the pliant flesh and Callie threw her head back and arched her back into the touch. She heard a soft whimper come from Callie as her head came back forward and her lips hungrily attacked Mark's again.

Arizona could taste the blood in the mouth. Apparently, she managed to bite her lip just a bit too hard. She didn't want to watch, but she found she couldn't look away. The object of her affection, so close to her, yet so far away, if she wasn't so frustrated she might have found this entire situation poetic, or at least a little ironic.

Mark stepped to Callie's side and turned her so that her back was pressed to his chest. They were both facing Arizona's bed and all Arizona could see was Callie's beautiful face. Her eyes were closed and her brows furrowed in concentration. Mark's hands drifted down her chest to the hem of her shirt and he tugged it upward, Callie getting the idea quickly raised her hands and he pulled the shirt off and then made quick work of her bra. Arizona gasped softly as she stared at Callie's heaving chest right before her eyes.

Mark leaned his nose into Callie's neck and kissed her softly as his hands moved to palm each of her breasts. He kneaded her breasts firmly before taking each nipple within his fingers and tugging softly. Callie whimpered softly and turned her face so her cheek brushed against his. "Just imagine I'm her," Mark whispered as he kissed her earlobe and then pulled it between his teeth to bite it, and then soothed his tongue across it.

"Maybe I could if you would shave once in a while…" He laughed softly and tugged on each of her nipples again and then pressed his palms against her nipples, gripping her breasts. Callie bent herself, pressing her ass against his crotch and feeling how aroused he was by the hardness pressing against her ass.

Arizona's eyes were wide as she watched the scene unfold right in front of her. She wished she could make out what was being said between them, but that thought didn't stay in her mind for long as she watched Mark feel up her best friend. She felt her mouth go dry at the site of Callie's nipples hardening and the dark brown patches of skin disappearing under Mark's hands. She couldn't believe this was happening and she felt powerless to say anything to stop it.

Mark's hands started to slowly move down Callie's chest. His fingers softly ran under her breasts and then then down her sides to the top of her jeans. He slowly moved his hands along her mid-drift to her navel and then further down with his right hand, which stopped at the button of her jeans. He worked the button open and she swatted his hands away, her own hands working the zipper down as she glanced toward Arizona. Arizona quickly shut her eyes and pretended to sleep for a few seconds as she listened to the zipper opening and then pants falling to the floor. When she opened her eyes again, Callie was pulling her pants and panties off and Mark had dropped his pants and boxers to his ankles. He stepped out of them and Arizona saw his engorged penis ready for action. She would have turned over and just tried to go to sleep after seeing that, but watching Callie had just aroused her too much.

Callie gripped the end table next to the couch. She was facing Arizona's bed and slouched just slightly over the table. Her arms were locked over the table, giving them stability and giving Arizona an amazing view of her breasts. Mark stepped behind Callie and placed one arm on her waist and stroked his organ twice before using both hands to work a condom on. He tugged at the top of the condom and then leaned forward as Callie turned her head to see what he was doing, ending up with his mouth pressing over hers. She heard them both grunt as Mark entered her from behind. Callie whimpered softly as he worked his way out of her and then thrust back in again. She felt her breasts jiggle in the motion and sucked his lower lip into her mouth as he thrust into her again.

Arizona's eyes were glued to Callie and she hadn't even realized her own hand worked its way between her legs. She watched how with each thrust Mark made into Callie, Callie's breasts would bounce forward giving her the perfect view of Callie's nipples, which were hardened into two peaks. Arizona licked her lips and imagined what it would feel like to taste them. At the same time, Arizona slid the index finger of her right hand through her tender folds, not surprised at the vast amount of wetness she found there. She dipped her finger into her opening and then pressed it deep within her. She opened her mouth in a silent moan, all the while watching Callie and imagining it was Callie's finger deep within her.

Mark was looking down, watching his penis as it left Callie's body, only to be thrust deep within her again. He was grinning like an idiot, obviously pleased with himself and his prized 'little Sloan'. He offered a firm grunt with each thrust, the rhythm quickly gaining pace. Callie rolled her eyes as she realized he was no longer really paying any attention to her and she was no longer even involved with the sex, just a wet hole for him to pour himself into. She licked her lips and then pulled her bottom lip into her mouth as her eyes made their way to where her extremely beautiful best friend was sleeping. She closed her eyes for a moment, imagining it was Arizona touching her, Arizona's fingers being pressed into her body, Arizona's tongue touching her skin. She couldn't stop the soft moan from escaping her lips as she opened her eyes.

Suddenly, she felt as though she couldn't move. Her deep chocolate brown eyes met the glorious sapphire of Arizona's eyes, only they weren't bright like usual, they were dark blue and Callie could tell Arizona was aroused. Neither looked away from each other and it took Callie a few seconds to realize Arizona was subtlety moving and then it clicked. Arizona was touching herself while Mark was fucking her from behind. She whimpered at the thought and smiled at Arizona.

Arizona couldn't believe she was just caught and she almost pulled her hand away from herself, but then Callie smiled at her and it took all of her strength not to cry out. She just locked her eyes with Callie and offered her a shy smile as she continued to press her finger into her wet core. She used her other hand to start gently stroking her clit while watching Callie. She licked her lips and watched as Callie did the same. She whimpered so softly to herself at the look Callie was giving her and she felt her orgasm creeping closer.

Callie was so locked onto Arizona, her mind decided that Arizona was making her feel so good, not the man behind her. She felt Mark spread her legs wider and his arm came around her thigh so that his fingers could find her clit. He started stroking it in time with his thrusts and Callie let out a soft moan at the end of each thrust. Arizona's jaw had dropped as she watched Callie pull her back up just a little and thrust her chest out a bit while smiling at Arizona. Arizona could see just how hard Mark was thrusting into Callie by how far Callie's breasts would sway.

Arizona couldn't believe how beautiful Callie's body was as it was flushed from the actions happening in front of her. Callie's skin was luminescent under the moonlight which crept in from the window because of the sheen of sweat she worked up. Arizona wished she was the one that made Callie's skin wet with heat and dark with arousal and the way Callie was staring at her, she almost felt like she was. She was definitely under Callie's spell and she could feel herself about to come undone. As the thought crossed her mind, she watched as Mark grabbed Callie's hair and pulled back roughly, giving Arizona a clear view of her beautiful neck and chest. He growled softly and then cried out as he finished, his hand carelessly rubbing at Callie's clit until she came undone seconds later.

Arizona's eyes widened as she watched Callie's body constrict in pleasure, Callie's eyes staring at Arizona with her mouth ajar. She went as far as to whisper Arizona's name in a soft gasp which brought Arizona over the edge. She felt her body tingle all over and pressed her chest out as her orgasm rode its way through her body. Callie was smiling at her as Mark walked a step away from her and picked up his clothes. "I told you that you'd enjoy it more if you thought about her." He winked and walked off to the bathroom to clean up and get dressed. Arizona was a little confused by what Mark had said, but she was still staring at Callie and Mark was so into himself that he didn't even realize Arizona was awake and watching them.

They stared at each other for another few minutes and then Callie offered a lop-sided grin before she picked up her clothes and dumped them on the couch, then put on some panties and a t-shirt to sleep in. Mark walked out of the bathroom and winked at Callie and then whispered, "Thanks for the good time, I'll talk to you and Blondie tomorrow." He waved and then left the apartment. Callie quickly locked the front door then went to the bathroom. She came out a few minutes later and crawled into bed, turning to look toward Arizona. She wanted to say something and was about to when she realized Arizona had rolled over leaving her back facing Callie's bed. She sighed and thought to herself, "Well, tomorrow morning is going to be awfully awkward…"