A/N: AU; Barney and Lily never 'slept together' at the end of S02E05; the deviations will become clear... (I will admit I stole the idea of 'firsts' from a Bucky/Darcy (Captain America/Thor) fanfic, however unfortunately I didn't favourite it and can't recall the title or author in order to credit them, so sorry, but I loved the layout of your fic so much I'm borrowing it for this one! I figure since it's a totally separate fandom it's okay ^_^)

The first time Lily helped Barney get rid of a conquest the morning after it was a complete accident; the girl saw her and assumed Lily was his wife. It worked so well that Barney asked her to stay, and in exchange all she had to do was pretend to be his wife to any girls that needed seeing off. Lily was a great actress, exaggerations in all the right places, and Barney was expertly capable of improvisation when she added little details to the act. They made a good team.

The first time Lily actually went out with him it meant putting a stop to the morning after act in favour of having a wing-(wo)man. The exchange was worth it; her success rate was phenomenal, showing a 42% decrease in the amount of women he had to approach before succeeding on a night out, on average. Plus, she had the 'bro-ette' advantage of talking in the ladies restroom and weeding out the crazies who didn't understand the concept of the one night stand.

The first time Lily decided to 'go out' go out, Barney helped her just as she helped him. He made a judgement on guys through casual conversation at the bar, just as she did in the ladies toilets, they exchanged info, then worked their respective magic. She came back the next morning, hair dishevelled, still wearing last night's skimpy outfit and smelling faintly of aftershave. He high-fived her as she walked in, strangely proud of her; she was already better than Ted as both a wing-man and someone to wing-man for, even if she was a woman.

The first time they both stayed in on a Saturday night was the day it should have been Lily and Marshall's anniversary. Robin had offered to take Lily out for the night to take her mind off it, but Lily politely declined, saying she'd rather be alone. Barney had overheard the phone conversation; he spent enough time with her to see through the lie, knew it was because Lily couldn't bear to spend time with someone so happily in a relationship, even if Robin was her best friend. So he did all he could think to do - bought Lily's favourite raspberry and white chocolate ice cream, put on his suit-jamas, and informed Lily she had no choice but to watch movies with him for the evening. All she said to him was "Fine, but I am not watching The Karate Kid again", but Barney could see the 'thankyou' from the way her smile met her eyes when she looked at him.

The first time they slept together was under the influence of alcohol. It had been a lame few weeks for both of them; the spring months full of new couples, pickings far slimmer than usual. After the 4th weekend in a row striking out, they were walking home as the suggestion arose. Of course, each swore it was the other's idea afterwards, though in truth neither could really remember enough of the night to know who was right. It was weirdly not weird; the deed was done, the morning after Lily gathered her clothes and wandered to her own room without commenting, and they carried on as normal. But from then on, it was a silently agreed deal that if they both failed to pick up for the night, they would simply go home with each other.

The first time Barney gave up a sure thing in favour of Lily, she didn't realise. The blonde haired... Wendy? Wanda? Willow? had gigged at even his lamest jokes, staring raptly at him as she sipped her 4th piña colada despite the fact he was paying next to no attention to her. Instead his eyes gazed across at the red-head by the jukebox. Lily was brutally unaware of Barney's situation, herself attempting to get the attention of one Maxwell Davidson. Unfortunately, Maxwell kept talking about how his ex Winona was at the bar that night, blind to Lily's obvious attempts at affection. She left early and dejected, not giving a second thought to the fact that she barely got 20 foot down the street before Barney was beside her, an arm casually around her waist and asking "No luck tonight either, Lil?" with a half smile.

The first time Lily gave up a sure thing in favour of Barney, he wasn't actually there. It was a teacher's evening out, her first since starting work again when the school year began, and there was a new 2nd grade teacher at her school. They'd flirted a little before, in the corridors and over lunch, but nothing had come of it. They were the last two in the taxi home at the end of the night, and as they pulled up to his block he handed the entire fare plus a hefty tip to the driver, winking at Lily and offering for her to come up for a coffee. She got out, wordlessly stepping onto the sidewalk, but as he leaned in to kiss her she backed off. "Sorry, I, I just remembered I have to go and, um, sorry," before half running the rest of the way home with a slight frown of confusion at her own actions fixed to her face.

The first time they said 'I love you', neither of them thought the other meant it, not like that. Lily had just got home from work, rushing back as she did these days to avoid spending unnecessary time in the staff room, and found Barney still laid up on the sofa, coddled in a sea of blankets and surrounded by empty herbal tea mugs.
"Awww, is someone still ill?" she crooned sarcastically across at him as she hung her coat up.
"Shud uhp, I feel like crab," came the reply.
Lily rolled her eyes, but busied herself with making a fresh banana and honey milkshake to sooth the ongoing sore throat situation.
"I lobe you," he said, gazing up at her as she handed it to him.
She kissed him on the forehead swiftly, "I lobe you too, Barney," she smiled, and he laughed in spite of himself.

The first time they properly kissed without having sex, it was almost a little romantic. Breakfast had just been finished, and Lily was preparing to leave for work, her last day before winter break. He caught her by surprise as she carried the plates across to the sink, spinning her around and initiating this incredibly deep kiss from out of nowhere.
"Mm, Barney, I really don't have time-", Lily began, almost dropping the crockery in surprise.
"That doesn't matter. Can you just... Shush, for a minute."

The first time anybody else knew about their 'not-relationship' as they called it, it was an accident. Robin had popped round to return Lily's Christmas jumper, which she'd borrowed back when it actually was Christmas, for a festive party. Lily had excused herself to use the bathroom, but when she returned it was to find Robin holding Lily's phone with a frown on her face.
"You just got a text from Barney, asking if he should bring chinese in for dinner."
"Oh," Lily held out her hand for her phone, "Thanks." Robin did not give it to her.
"Why are there kisses at the end of the text?"
"Oh, you know, kisses are friendly, I send kisses to everyone," Lily smoothed her hair behind her ear, trying to cover her flustered nature, "You, Ted, Barney, there's nothing odd about it at all."
Robin raised her eyebrows, "Yes, you send kisses to everyone. Barney doesn't send kisses to anyone."
"But, it's just-"
"Lily?"

The first time everybody found out about their relationship officially, they even held hands.

The first, and only, time Barney proposed, it was two years later. It wasn't flashy or extravagant, because Lily wasn't flashy or extravagant. It was elegant and understated and perfect. He didn't pick some significant date, either, she just came home one day to find the apartment in darkness, a pathway of white lily petals leading towards the bedroom with a border of little tea-light candles lighting the way. The bed too was covered in petals, the same custom made Italian blue ones they had picked out when she very first started living there, and Barney was simply sitting on the edge, ring box resting open on his knee. He stared up at her as she came to a stop in front of him, his mouth opened but no sound came out, his suddenly wide eyes full of the question he couldn't begin to put into words.
"Yes," Lily whispered.

A/N 2: Okay, so, for anyone who follows me as an Author and is reading this, I know I said I was working on a Once Upon A Time fic but I have so much uni work it's ridiculous, so chapter fics are gonna have to wait a while I'm afraid :( But I couldn't resist writing this, been wanting to do a Lily/Barney one for ages and I had this idea stuck in my head ever since I read the Darcy/Bucky one I mentioned in my first author's note.
Thankyou to anyone who reads and reviews this, I understand there's a very small ship for this pairing considering the size of the fandom as a whole, so any feedback I get will mean a lot! :) xXx