Written for my good friend EB (Distancetoearth on Deviant Art, Therebemorefoolery on tumblr) at my main blog on Tumblr; the Stinky Foot wrote a very nice story for EB's AU wherein Finn is the Vampire King and Marceline is a human; for more information, it's best to check out her deviantart site and check out her pictures for it, there's way more detail there than I can think of off the top of my head.
Mostly written beecause Stinky's extremely good writing for Finn was still bouncing around in my head, and also because I thought Finn would have a bit of a situation about being forever on the young side of teenager-dom.
Disclaimer: I do not own Adventure Time, or make any profit of this.
"Peter Pan?" Marceline the Human said, and laughed; not like she thought it was ridiculous but like she didn't get it and though that this was funny. "The heck is that?"
Finn had been Vampire King for longer than he really bothered to remember – long enough for blood to flow from his hands to dam a river, a whole tide of evil ended and broken by his hands so maybe it was good that he'd been around so long anyway – but he still blushed just like a little kid. He hovered up so he was a head higher than her, because it was just so embarrassing standing up next to her and having to look up and up to see her face and oh didn't she just smirk when she saw where he stared for bits and moments at a time.
And Finn laughed, and grinned; his fangs made little clicks where they came together, clik-clik. "It was a story I heard when I was a little kid, long before the… the war."
He always stopped, always stuttered before he could talk about that. The War. The Great Mushroom War. His heart hadn't beat like a mortals in a long time, but it always paused a few electric beats just thinking about that. For a long time, he couldn't say anything at all. He managed himself, and he continued, "It was a story about a kid who could fly, and spent forever fighting with bad guys, and he never ever could grow up."
Marceline's palm went up to her chin, and he just stared at how she could cradle herself. Sometimes he wondered if she even knew how cool she looked, if she ever had to think about doing the right little motions or if she was just awesome all the way through down to the bone and blood so it showed in everything she did (and Finn hoped like all the crazy things that she never saw how his little flips and tilts when he hovered around her was really him kinda-sorta swooning a bit, she could just make his heart speed up and start really being alive again and she just didn't even know).
He didn't realize she was talking for a few seconds. "-Sounds just like you," Marceline was saying, and Finn zoned back in.
Finn laughed a little bit, like the sound of the wind rasping on small spiky rocks. "Yeah, maybe, I guess."
And now Marceline was looking up at him. She frowned a little bit, lips dark in the night and brown-ish skin illuminated like a backdrop from the pale moonlight. "…Huh. Does that ever bother you?"
Finn was slowly revolving in the air, back facing the ground several feet below, and he blinked a few times before the sense of what she said got to him. "What does?"
"Being like Peter Pan, I guess." Marceline wave a hand vaguely. "Never growing old. Watching your buds grow old. Things like that."
Finn stared at where her hand had gestured, some random point towards the forest.
(There is a place far from here, far from war or death and blood to touch, and there are small rocks piled neatly together, spiraling out from a single name that still lives but is lost to him – Simon Petrikov – and all around it are rocks with the other names, names of people he watched wither away back into the dust or die standing like heroes, or cut down by monsters for no reason. He stopped asking why long ago, he just learned to live with it, and remember them.
He still cries sometimes, when no one can see. It's like letting poison bleed out; it hurts and how it aches until part of him just wants to explode, but it feels better when it's done, but still so sore.)
"Yeah," Finn said after a long moment, a certain coldness welling up in the tips of his fingers. "I guess so."
Marceline stared at him for a long time. He had no idea what she was thinking, he never knew what she was thinking, she was like the neatest little puzzle box, always changing on him and never the same but still the same passions under the shifting surface, and she broke him right out of his brief thinking spell by punching him in the shoulder; he was tough, tougher than all the other vampires and strong enough to kill the Vampire Queen ages and ages ago, but that punch still hurt, bruised him down to the muscle-
He grinned. It felt good.
Marceline laughed, and clapped him on the shoulder. She leaned up, and Finn hovered a little bit down. "Betcha I can still get a good reaction out of you, old man."
He sputtered, "I'm not old!"
She leaned in closer, and Finn suddenly felt very hot in the face. "Really."
"Really!"
Her breath was on his face, and suddenly her lips were on his nose, a quick kiss right there, a sight faint pop when she tilted away, a slightly surprised look on her face like she had scared herself a little, and Finn made a small squeak of surprise and crashed right to the ground.
"Told ya," Marceline said as Finn looked up, and she loomed over him; he was older than her, by years and years, but she was physically older than him, and he would never be catch up to her like that, and for a second he thought it was kind of nice to have to compete like that with someone.
She punched him in the shoulder again. "Come on," She said, and Finn hovered up again. "Tell me more about this Peter Pan thing. I wanna know all the awesome things."
Finn hovered down to a rock and sat down, forever fifteen or fourteen or whatever age he was, he honestly forgot years ago, and his friends don't mind so he stopped caring too even if it creeped out too many girls he started to care about but Marceline doesn't care because she's just a few years older, and he tells her everything he can remember about the story, and makes up the stuff he can't remember or when it would be cooler.