All at Once

Summary: Sisters Lexie and Meredith Grey meet friends Mark Sloan and Derek Shepherd at a bar one night. Meredith and Derek hit it off right away; Mark and Lexie, not so much. In fact, they don't even like each other. She can't stand his man-whore ways and he hates her rigid personality. But when her sister and his best friend start dating they are forced to spend more time together. A/U Slexie all the way, but contains some MerDer. Rated M for language and smut and other adult themes in later chapters.

Author's Note: Take place around the time of the merger, though many of Grey's Anatomy events have not happened yet; particularly the ones that center and Mark/Lexie and Meredith/Derek.

All at Once Chapter One

"Why are we here again?" Lexie Grey asked her older sister as the sisters sat down one the two bar stools at the end of the bar, giving them the most privacy they could have at the bar. "We start at the new hospital tomorrow. We shouldn't be drinking. We should be studying or watching the latest surgical tapes. Or…"

"Lexie." Meredith held a hand to cut her younger sister off, "You need to relax. We both do. That's why we are here. We are going to have a few drinks and then tomorrow we are going to work and we are going to kick ass, okay?" She sighed when Lexie didn't look convinced. "We are Grey's and we are going to kick ass tomorrow. Okay?"

Lexie nodded, "Okay. Okay, you are right. We are going to kick ass. Besides we are probably be going to be spending a lot time here, since it's so close the hospital." She took a look around their surroundings. The bar was fairly empty that night; there was only about half dozen other patrons. She wondered if any of them were doctors at the newly named Seattle Grace Mercy West Hospital. She flagged down the bartender, "First round is on me."

"Tomorrow is the big day." Derek Shepherd grinned as he, and his friend Mark Sloan, took a seat at the bar at Joe's. "You nervous?" He asked as he grabbed his wallet out of his jacket pocket, pulling out a twenty dollar bill and tossing it down on the bar.

Mark laughed, "Oh yes. I am so nervous." He said sarcastically, "I'm excited. I'm one of the best plastic surgeons in the country and tomorrow the hospital will be getting how many more new women doctors and nurses? Ones who won't think twice about hooking up with one of the country's best plastic surgeons, I won't even have to try. Tomorrow is going to be a wonderful day."

Derek rolled his eyes, "I really should warn them all about you." He smirked, "But I'm sure the women you have already slept with will do that for me." The two women sitting at the other side of the bar caught his eye, particularly the blonde woman who looked to be a few years older than the brunette. The brunette must have said something funny because the blonde began to laugh. Her laugh was nearly intoxicating. He almost frowned. He had never thought of a laugh attractive before. But hers was. "Mark, do you see those to women over there?" He asked as he gestured toward the two women.

Mark glanced to his left. "I do." His gaze immediately shifted to the brunette, a small smile played on her lips. "I call the brunette."

"That's fine with me because I like the blonde." He waved Joe over, who was the bartender and owner of the bar and ordered drink for Mark and himself and told Joe to give the women another of whatever they were drinking.

"Here you go ladies." Joe placed another whiskey in Pepsi in front of Lexie and a tequila sunrise in front of Meredith.

Lexie frowned at the drinks, "Thank you, but we didn't order these."

Joe smiled. "I know. They are the complements of those two men right there." Joe gestured towards Mark and Derek, who smiled and waved at the two women.

Meredith smiled back, "They're cute." She whispered to Lexie, "I like the one with the amazing hair." She said, referring to Derek, "We should go over there. Thank them for the drinks."

Lexie sighed; she really did not want to go over there. She didn't even want to go out tonight; she just wanted to concentrate on starting at a new hospital the next morning. But she also knew there was no point in arguing with Meredith, "Fine." She grabbed her drink and purse from the bar, "The other one is hotter anyway." She smiled, "Do you think that's the way they intended it? Because it is going to be awkward if it isn't." She joked.

"Hi." Meredith greeted to men, "Thank you for the drink. I'm Meredith Grey." She introduced herself, putting her purse on the barstool next to Derek, "This is my sister Lexie."

"You're welcome for the drinks." Derek smiled back at Meredith, "Derek Shepherd. This is Mark Sloan."

Lexie smiled nervously at the friends. "We will have to get the next round." She told them taking a seat next to Mark; she could clearly see that Meredith and Derek were hitting it off. She gave Mark another nervous smile, "Looks like you are stuck with me."

Mark smirked, "I wouldn't call it stuck." He looked down at her drink, "What are you drinking?" He asked curiously.

"Whiskey in Pepsi." She told him before taking a quick drink, "I don't mean to be rude, but how old are you? You don't look like you should have the salt and pepper hair quite yet. Did you go gray early?"

"I'm thirty seven. started to go gray in my twenties." Mark explained to her, "People seemed to like it, so I kept it that way." He paused, "How old are you?"

"Twenty six." Lexie answered, twirling her straw in her drink. "Do you come here a lot?"

Mark nodded, "I do. It's close to work, so I will come here a lot after work."

"What do you do?" Lexie asked before taking another drink.

"I'm a surgeon at Seattle Grace."

"Oh." It suddenly dawned on her. Mark Sloan. She knew the name sounded familiar. She knew him for two reasons, the first being he was a world famous plastic surgeon. And the other, "Oh." She repeated, "You're that Mark Sloan." She sighed, hoping Meredith was having better luck with Mark's friend. She just hoped Derek didn't have the same reputation as Mark.

"You've heard of me?" Mark smirked with a raised eyebrow.

"I'm friends with Tracy Flannigan." She quickly became annoyed when a look of confusion appeared on Mark's face. "You slept with her and never called her again."

Mark smirked, "You are going to have elaborate a little bit more. That is pretty much every woman I sleep with."

"She's blonde." Sighing when the description still didn't seem to jog Mark's memory, "She has really big boobs." She said while mimicking big breasts with her hands. "I mean really big."

"Oh yeah, Tracy. I remember her now." Mark grinned when he saw the look of annoyance etched on her face.

"Figures since you are a plastic surgeon you'd be a boob man." Lexie mumbled with an eye roll, turning her attention back to her drink.

"How did you know I was a plastic surgeon? I just said I was a surgeon. I don't remember ever telling Tracy my specialty."

"I like to keep up on any cutting edge surgeries; your name seems to come up a lot."

He raised an eyebrow, "You thinking of a boob job?"

"What? No!" She sighed in disgust. "I'm a second year surgical resident. I like to read up new techniques. I start at your hospital tomorrow. Crap!" She groaned, "That means you are my boss." She quickly downed the rest drink.

"You know, if you sleep with me I can get you into some pretty stellar surgeries." Mark joked, but quickly realized Lexie did not take it as one. She looked absolutely disgusted with him. "Hey, relax. I was joking."

"Sure you were." Lexie muttered, turning away from him. "You are disgusting, you are aware of that, right?" She asked annoyance evident in her voice.

Mark shrugged, "I've been called much worse than disgusting, sweetheart." He smirked, deciding to annoy her further; wondering how far he could take it, "So you wanna get out of here? My apartment isn't far from here." He laughed out loud when her face twisted in disgust, "You are way too easy."

"And you are an asshole."

His smirk broadened, "I'm your boss; you can't call me an asshole."

"I think I just did asshole." Lexie shot back in glare.

"Lexie!" Meredith's voice scolded. Lexie whipped her head around, seeing her older sister and Derek standing behind her and Mark. Meredith's hands were on her hips, "What is going on here?"

"He's being a total asshole."

Meredith sighed, "You do realize who these guys are right? Mark is one of the best plastic surgeons in the country and Derek is one of the best Nero surgeons." She smiled at Derek, "It is following his work that made me interested in Nero as a specialty. And we are going to be working with them."

"Just because he is one of the best plastic surgeons in the country doesn't mean he is any less of an asshole." Lexie quickly argued.

"Stop calling him an asshole." Meredith argued back, "He is going to be our boss. You can't call him an asshole." She tried to reason with her younger sister.

Mark crossed his arms over his chest, an amused smile playing on his lips, "That's what I told her."

"Shut up." Lexie snapped, rolling her eyes. "As you can see we aren't at work. And technically he isn't our boss, so tonight I can call him whatever the hell I want." She told the group stubbornly.

"She's got a point there." Derek smiled softly, trying to break the tension that Mark and Lexie created. "Besides, I've known Mark for a long time. He can be asshole."

"Thanks buddy." Mark thanked his friend sarcastically.

"I'm leaving." Lexie said, grabbing her purse off the bar. She forced a smile, "I guess I will see you all at work tomorrow."

"Lexie…" Meredith called after her sister, "Don't leave. Come on, I'll buy you another drink."

Lexie shook her head, "No. I just want to get home. I'm tired. I'm stressed. I just want to go home." She looked past her sister, "It was nice to meet you Derek." She shot Mark a dirty look, "Don't stay up too late Mer."

Meredith sighed, "Okay, go get some sleep. Hopefully tomorrow you'll be in a better mood." She muttered as Lexie turned and walked out the front door of the bar. Meredith turned to the two men, "I'm sorry about that. She really isn't normally like that. She's just stressed from this whole merger thing. She'll be better once she gets used to working at a new hospital. I promise."

Derek smiled, "I'm sure Mark didn't help matters." He shot Mark a look, "Exactly what did you say to her to piss her off so much."

Mark shrugged, "Apparently I slept with one of her friends and never called her after."

Derek rolled his eyes, "I see your reputation precedes you." He turned to Meredith, "You still want to get out of here?"

Meredith smiled, nodding. "I'd love to."

The next morning Lexie carefully maneuvered around the still packed boxes she had strewn around her new apartment. She had moved in the previous weekend and had yet to fully unpack. She sighed, it had been yet another reason that she should have stayed home the night before. She hated clutter. And depending how her first week at Seattle Grace Mercy West hospital went she didn't know when she would have time to finish unpacking.

She tried not to think of the night before. She honestly dreaded seeing Doctor Mark Sloan again. She had spent all of twenty minutes with him last night and he had infuriated her more than anyone had in a long time.

Jerk. She thought bitterly as she poured the rest of the coffee that she had made earlier that morning into a travel mug. She glanced at the clock on the wall. She had to go now or else she would be late. She was thankful that her new apartment was just across the street from the hospital. It was only a five minute walk. She grabbed her purse off the counter and headed out the door. Once in the hallway she turned around, locking the door behind her. She smiled slightly when she heard the apartment door that was across the hall from her open, "Finally, I get to meet one of my neighbors. I'm-" She cut herself in stunned silence when she turned around and saw who emerged from the apartment across from hers.

She blinked; hoping vein he was just a mirage and would disappear. "You have got to be kidding me…"

There he was; standing in front apartment 19 with an over amused smirk on his lips.

Mark fucking Sloan.

"Please tell me you are just leaving a one night stand and this is not your apartment." Lexie nearly pleaded with him.

Mark grinned, "No such luck. Neighbor."

This is my first Grey's Anatomy story, so please by nice. Reviews are more than welcomed; if you like please review. I hope to have more up really soon.