Insert obligatory "I don't own Adventure Time" statement here. This is also kind of a songfic to Taylor Swift's "Mary's Song (Oh, My, My, My)" which I'm also obv. not affiliated with.

Take me back to the house in the backyard tree

Said you'd beat me up – you were bigger than me -

You never did… You never did…

Fionna the human and Marshall Lee the vampire were always the best of buds, almost since the day the met (Almost. There was a learning curve). It began when she was about thirteen, and his thousand-and-something-year-old self just popped into her life without warning. And when he did -

He'd scared her.

Threatened to drain the blood from her body.

Left an…eerie feeling in her house, even when he was no longer there.

But he never actually carried out any of his "threats".

Of course, all of the things he did do would make any thirteen-year-old somewhat uneasy, no matter how many monsters they'd battled. But there was something different about a vampire. Based on the stories Cake had told her, coupled with what Fionna had experienced herself, she knew that they could defy gravity, turn invisible, transform into a number of terrifying beasts, and – worst of all – they did drink blood.

Or… did they?

It seemed like everything she thought she knew about vampires was turned upside-down once she started to get to know Marshall Lee. Well, he could do all of the above, except for the fact that he chose not to drink blood. Instead, he drank the color red out of apples, strawberries – you name it! - and that was endearing, in a way. After all, the fact that someone had more than enough potential to be horrifying and evil yet chose not to meant they had a soft side, right? And as Fionna continued to get to know him, she realized he wasn't all that scary. Yeah, he was kind of an ass, always coming on to her solely for the purpose of making her feel uncomfortable and awkward, but he was actually pretty cool, too. He wasn't like PG who would stay at home and bake and get excited about that stupid junk, and he wasn't like LSP who would call up everyone he knows just to complain about how difficult his girlfriend or ex-girlfriend or whoever was being…

Nah, Marshall was a total bro. The kind of dude who she could play BMO with and she could yell and act like a doofus with just playing a stupid game, and he wouldn't judge her for screaming at a screen. The kind of dude she could eat tons of food with and get it all over her face (because, what use are napkins when you have a tongue to lick the mess off?), and he'd make an equal mess of himself. The kind of dude who would go out and get messy on adventures with her – punching through goopy monsters and getting tossed into the mud and not really caring, because he wasn't some prissy prince who – Glob forbid dirt touch him! The kind of dude who she could punch in the shoulder and he'd punch her right back, and they'd laugh. The kind of dude who she could vent about that stupid pink prince and how she totes had the hots for him but she was "too young", and why should that even matter? - and he'd totally take her side. He was even more helpful when it came to her conflicting feelings involving Flame Prince.

Yeah, the were buds.

So it was a little weird when one day, just after she'd totally annihilated him playing some racing game on BMO at the treehouse, she'd somewhat shyly asked, "Do you think I'm too…y'know…dude-ish?"

Marshall raised an eyebrow. He had to keep in mind that humans, especially females, were full of conflicting emotions. It was better to just go along with what they said – just agree with them…usually. "Meaning?" he prompted, wanting to make sure he understood her completely before making judgement (girls were terrifying when they were mad, and he didn't want to get this wrong!).

"Well, y'know. Obviously I'm a girl, like, duh, but I don't always act like a girl, y'know what I mean? I dunno, I mean, I don't really care myself, but do other people think it's weird?"

Marshall just laughed. "Dude, this isn't funny!" Fionna's voice was raised, and she flushed a little.

"Sorry," he chuckled, "It's just that, that's a kind of stupid question." Fionna became redder, but in an angry kind of way, and her face scrunched. "Look, I just mean that everyone's always known you as, well, exactly how you are - willing to fight the guts out of evil, not afraid to get messy… if you were to suddenly act all girly, I think it'd throw everyone off, y'know?"

"Yeah," she sighed, "It's just that sometimes I see other girls gettin' all fancied up, going on dates or whatevs-"

"You mean Cake when she goes to see Lord Mochro."

"There are other girls I see around! Sometimes…. But yeah, sometimes I feel like I should be doing that too. I dunno." Suddenly, Marshall bonked her on the side of the head- hard. "OW! The junk was that for?!" Fionna yelled, holding her now pounding head.

"Oh, sorry, dude, I thought you were maybe possessed or something, since you weren't exactlyacting like the Fionna I know. I mean, the FionnaI know wouldn't give a crap about what anyone else thought. She wouldn't care if she was acting too girly or too dude-ly. She'd just care that she was acting like herself."

"Oh." Fionna let go of her head, "Yeah. I guess I was thinking stupid. That's totally never happened before, though…what the junk is going on…" she mused.

"Maybe you have poo brain." His comment was met with a rough punch to the arm, but he laughed. "Okay," he tried again, "I happen to remember, from like ages ago, that sometimes, human chicks would act pretty weird every few weeks…any chance-" he started to smirk, but that comment was met with a very powerful punch to the face (he took it as a confirmation).

Yeah, they were bros.

Well, I was sixteen when suddenly,

I wasn't that little girl you used to see -

But your eyes still shined, like pretty lights

Humans aged mega quickly. At least, they seemed to when you were a vampire who'd been around for ages. So it was a bit shocking when suddenly fourteen-year-old Fionna turned fifteen, sixteen, seventeen… She was nearly eighteen now – eighteen! That was a big deal pre-Mushroom War! - and things had changed. Sure, she still went around fulfilling quests, slaying monsters, finding treasures – but some things had changed. Like, since when had she started caring about her hair? There was a time when she'd grown it out to the point that it was a tangled mess, then shaved it all off, then grown it out again – but these days, she tended to trim it, keeping it under control…. but it was still pretty. Then there was the fact that – and this had taken Marshall a while to figure out – she would sometimes wear make-up! Ok, so it was just foundation, and it was only because she'd gotten that one little zit and she was probably just embarrassed from that whole ordeal (which was all LSP's fault, by the way) and didn't want the same thing to happen again, but still!

And then, there were things about herself that she hadn't changed, but that nature had. She suddenly had these more…defined features – a more hourglass figure, high cheekbones – wait, was she plucking her eyebrows now? No – Marshall let out a breath – her brows just happened to naturally grow in a manicured-ish-fashion. Thank Glob, at least he didn't need to worry about that. Maybe it was because he was a guy, but he never understood why females would cause themselves pain in order to "look better". Of course, no matter how much Fionna changed and grew up, she'd never become that vain.

Still, she was slowly changing (he blamed the human – no, female reproductive system, because guys never changed that drastically), and he was not okay with it. After all, who was to say she'd keep being his bro if she gave in to her… feminine desires? One day she's wearing a little cover-up, the next she could be wearing heels and a little black dress! But on the other hand, maybe he was okay with all of this… it was those slight changes that had happened over the past several years that made him more interested her. Of course they'd grown closer since they'd first met – she trusted him now, and was pretty much immune to the way he'd try to come on to her – that was friendship...right? - but maybe he was more serious when he flirted with her now. Maybe he would have been okay if she'd said, "Yeah, alright, I do love you."

Ugh, what was happening to him?

As for Fionna, everything was suddenly confusing, and it seemed like it got more confusing the older she got. She wondered if she wasn't feminine enough a while ago, but Marshall Lee had dispelled that fear then. But then Cake was like, "Tell guys they're hawt! Wear more sexy clothes! Act….not like you, and they'll totally fall for you! No offense…"

So what was she supposed to act like? She felt conflicted – she wanted to keep going around kicking the guts out of bad guys, but anytime she was around any dude, she sort of felt like she should chill and just agree with him and be what he wanted. Every time PG called her, she secretly hoped he'd created a dessert with her in mind. Whenever Marshall Lee said he had a gig and wanted her to sing with him, deep down she hoped that maybe it would be a song for her. If Flame Prince came to see her, she thought that maybe he wanted to be with her again.

No, no, no. Every time.

"UGHHHH!" she screamed, pulling at her hair and flopping onto her bed. "What the junk am I doing!?"

"I dunno," Marshall appeared from nowhere, "What are you doing?"

"Really?" she deadpanned, "What are you doing here?"

"Really?" he mimicked her face, "Did you forget that, technically this is my house?" she glared at him. "Plus, I can turn invisible?" her face softened - slightly, "Plus, Cake isn't here to yell at me for some junk? Not to mention I haven't bothered you in a few days..."

"Doesn't give you permission to spy on me."

"You want me to help or not?"

Fionna sighed. "Well, not that I asked for it, but sure. Why not."

"I happen to be an expert on human emotions," Marshall smirked, "Who else do you have to ask for advice?"

"Alright!" Fionna exclaimed, "Alright. Please, give me your diagnosis." She said sarcastically, rolling her eyes. It sort of pissed her off that he could get in her head – how much spying did he do on them, exactly?

"Well," he sat next to her, "According to my prognosis, you're totally torn between your wanting to be a monster-slaying heroine and some chick who isn't afraid to wear frilly dresses and junk."

Fionna turned bright red. He was dead on. "N-No…Yes…" She covered her face. Marshall Lee laughed. "How'd you know?" she asked, peeking out between her fingers.

"Uh, you mean it isn't totally obvious?" when he saw the girl become completely flushed, he changed tactics, "I mean, you've changed since we first met, y'know? Like, you still beat up bad dudes or whatevs, but you're not afraid to…. enhance your attractiveness. By that I mean little things like how you do your hair and whatever."

Fionna laughed. "Um… haha… I guess you're right… I'm not sure why, but…well, sometimes I feel a little insecure," she started to open up, "I mean, not when I'm fighting gross-ass dudes who are trying to hurt some part of Aaa, but like, when I'm surrounded by princes and well, even you."

"What do you mean, 'even me'?"

"Well," Fionna twirled her finger in her hair. Marshall watched her figure as she swung her legs over the side of the bed. 'Okay,' he thought, 'She's kind of hot. But she's my bro, man, like, we hang out and stuff!'

"Well," Fionna's voice snapped him out of his thoughts, "You're not a prince like PG, LSP, Flame Prince, Wildberry Prince, -"

"Okay, I get it," Marshall cut her off, "Aaa is filled with princes. And me."

"I don't mean to put you on a different level or anything, I mean, I guess you're a 'king' or whatever but-"

"Fionna."

"Sorry, okay, like, whatever. I just meant that you're different from most guys I know."

Now Marshall blushed, but just a little – Fionna didn't even notice. "I'm closer to you than anyone else…minus Cake, of course," Fionna smiled for the first time during the conversation, but it quickly turned into a frown. "What do you think about me?"

"I-"

"And don't just say what I want to hear!" Fionna crossed her arms, "I know you've been with girls before the Mushroom War, and you probably just said what they wanted to hear – I know, I have books and junk to prove this! Guys are actually really lame," she muttered the last part, then spoke up slightly, "But I want you to answer honestly now," her voice softened and she looked away.

He thought for a moment. Women had conflicting emotions – and Fionna was practically, technically a woman now – how was he to respond without offending her and possibly loosing his best friend?

Honestly, now…

He sighed. "Well," he started, "It's totallyyou to kick butt and leave monster guts everywhere," she was opening her mouth to speak but he continued, "But, since you've grown older, you've also become more attractive and more available? …I mean, you're not a kid anymore, you know?"

Fionna sat in silence for a moment, then nodded, "Yeah, I guess you're right…I mean, I totally don'tlook the same, right?" she laughed.

'Well, yeah, duh, your boobs have grown. That's a big enough difference on it's own, especially to a dude!' Marshall Lee thought, but didn't say it, knowing she'd punch his guts out if he did. Instead, he said, "Your looks have changed – slightly – but you've always been the same person on the inside. The only difference is that you're hot now."

Fionna blushed. "Uh, what?" she gave a small laugh, thinking he was just teasing her.

"Uh…." Marshall paused, then realized it was too late to back out of what he said, and tried to play it cool. "Yeah, dude, you've got curves in all the right places, perfectly sized breasts, and you keep your hair in check – not like when we first met. Why, you're practically the kind of girl I'd go out with way back when." He mentally slapped himself as soon as he'd said that. Why had he said that? It was meant to be a joke, but it was also true. Ever since she'd turned sixteen, he'd pretty much found her irresistible. Everything he'd wanted in a woman – sexy, but not fragile; not afraid to speak her mind, but also sweet- and more – it was all there in Fionna. He just didn't want to admit it.

So he was surprised but not horrified when, as he was looking away out of embarrassment (but only slight embarrassment, mind you!), she pecked him on the lips.

"Y'know," she said softly, "I've always sort of liked you." It was true. Even the part of her that didn't care what anyone thought about her wouldn't have minded going out with him.

"Well duh." he rolled his eyes sarcastically. He had tons of women after him – this shouldn't be a surprise.

Fionna punched him in the shoulder. "Ugh, why do I bother." she half-frowned…

And then, Marshall Lee kissed her. Luckily, neither felt the uncomfortable awkwardness one often feels when kissing their best friend. Maybe it was a sign from Glob, or maybe they ignored any such feelings so well that they didn't even register.

And just like that, it was over, and he was answering her what was meant to be rhetorical question. "Because I'm the only guy who'll accept you for exactly who you are? Because I appreciate that you're fearless and hot; that you can kick the guts out of me but you still care about how you look – sometimes. That -"

"Okay, okay, I get it," Fionna blushed. She didn't feel comfortable with Marshall Lee complementing her. It just wasn't something that he would do. But it was nice to know that her problems were basically solved – she knew what he thought of her and knew he liked her just so long as she was being herself – it was a perfect scenario, when she thought about it.

"Haha," he laughed. "So," he said, "You said you've always 'liked me'. Care to elaborate?" He still relished in making her uncomfortable, but she had grown used to his tactics, and knew exactly how to handle them.

"Sure," Fionna answered, "Just as long as you do something for me."

"Yeah?"

"You've written, like, a billion songs now. How come you haven't written one for me?"

Marshall Lee smirked, took out his axe guitar, and began strumming a tune.

Yeah they were bros. Bros who also happened to be going out.

xxx

This story got a little out of hand. I wanted to represent Fionna as how she's portrayed in the show, that, for the most part, she doesn't give a care about what anyone else thinks and is a pretty tough chick who does what she wants. But at the same time, being an adolescent female is hella confusing, and I wanted to show that she may be the heroine of Aaa, but she's still a human girl who possibly does have these insecure feelings sometimes. Fionna is probably the most difficult character to write because she isn't that stereotypical female in need of saving, but when writing a love story, that's the kind of character we tend to create.

Anyway, I hope I was successful in this. I'll be writing more in the future, most likely. Follow me on Tumblr (voguebishoujo) if you're interested!