If you're familiar with Fallout: New Vegas and, more specifically the DLC Old World Blues, you might recognize a few concepts mentioned here.

Disclaimer: I do not own Adventure Time or any associated intellectual properties. This is a work of entertainment without monetary gain.

Dust falls. She turns her head to watch it fall as what she was saying fades away, stillborn speech drifting away as her attention goes elsewhere, the light looking strangely lovely as the dust interrupts a path of illumination to create faint echos of shapes. Not patterns, not genuine ones, but they look enough like patterns that part of the mind declares they must be and makes up some anyway.

Her mind is attuned to details and introspection, study and looking for the patterns. And then, finding the truth. Truth is important; whether in the systems of how the laws of reality really work, the function of the force that it suited people to just call 'magic'... and less comfortable things. Truths that hurt. And it was cowardice to love one kind of truth and shy away from another. She'd learned early on, long before she put on the crown and the rival nations of Ooo learned to worry about what she might do next, that just because something hurt it only caused worse pain to pretend it never was.

(Face reality, however painful. Realities of things like lies and death and the end of an old world and the dissolution of so many beautiful things, they were terrible realities. But they were not the same as the truths of physics and biology and mechanisms and the functions of the mind; they were shifting things, fluid and the components of a better world. To realize this, was to conquer the illusion that things could not be changed.

Then you can change the terrible truths: tear them down, rip them apart, burn them to ashes and scatter them away forever. In their place, build something better and greater than they had ever been.

She had seen from an early age the mistakes of the old world did not have to be the future of the world they had. They could build something better. She would build something that meant something, even only for a time.)

The first analogy to cross her mind as the dust falls is not a flattering one, even perhaps inappropriate. She tries not to grumble under her breath, consternation rising inside against the feeling that it looks like dandruff falling off a celestial head. She almost snarls, indignant at her own instinctive thought processes. Shameful, rude, distasteful.

Her mind, in the circumstances, kept going into odd places. Here and now: she thought how strange it was that she chose that word to describe it and with such vitriolic dislike of impropriety the word choice suggested.

(She knew why, of course. She knew her own mind, and she knew her finest qualities as well as she knew her faults... even if she rarely cared to acknowledge the worst about herself. (Pride, something says to her in the night, in words that sound like something Finn might say if he had a bigger vocabulary, dances inside you. It has its own music to make you listen and ignore everything else, and maybe one day you might just say that the music is more right than the rest of the world so just damn them all because you know you're right... And the thought is a terrible one, suggesting things that she dares not think about in the light of day, and it is unspoken the terrible suspicion of what she might then become. Something far worse than the Ice King at his worst, more terrible than the Lich even, for the thought of herself swelled in hubris and blinded by self-righteousness awakens her to the terrors she might well unleash on the world for the sake of whatever she decides is better for the world. And it is then that she dreads what might become of her if Finn was suddenly gone and she was left alone to drift into illuminated solipsism, and no one left to tell her she was wrong.

Princess Bubblegum was a person of many qualities. Many of them ran counter to another; she had morality but very few standards of what might be considered ethical behavior, with pragmatic considerations in their place. In much the same way, she had a decidedly... perverted senses of scientific adventure and reasoning. It would not occur to her to stop doing something because someone else might find it disturbing: the thought would never occur to her.

And yet, a certain sense of propriety intruded often: a sense that there were something that just shouldn't be done because... she was at a loss to say why, exactly, but they just weren't supposed to happen.

With one hand she could twist the universe inside out just to see the tone of the noise it made, and with the other she scolded bad language because it was inappropriate to hear outside.)

Princess Bubblegum snorts again, and a stray thought arcs, a spark off a torch always primed for its work: she does not generally like the notion of dualities, and yet all too appropriate in this case. Half the time a mad scientist rising to ever higher highs of genius and wonders undreamt of by even those of the old world, and the other half a proper ruler held straight and stretched out on standards so harsh it was like being crushed all day long and she didn't know why she did it.

A wayward thought, and amusing: that she wasn't honestly sure which was the more genuine side, unaffected by the way her life went. A troubling notion, too.

Princess Bubblegum didn't realize she had actually said all that out loud, every single last word sounding off into the air in a single stream-of-consciousness ramble halted only by the occasional need to take a breath or a random thought pattern pushing her into another direction, until Finn looked up at her from the little makeshift chair next to her's and eventually said, "I think you worry about this stuff too much, Peebs."

She resists the impulse to clap her hands to her mouth and stifle a gasp or something of that sort. It feels too much like acting a part, these days. Her hands come together, squeeze, and her face colors, flushing shades of almost-red. She looks down, so that thick and blobby bits of gum-hair flop and bounce over her face, settling into place with a feeling like solid water knocking around.

She coughs. Just once. "Ah. I, did not intend to say that aloud."

She peeks up, just enough to see him tilting his head; with that compact frame, learned movements and the way his bearskin hat sits open his head so that the ears even look quirked in interest, he looks exactly like an interested puppy.

Only he's not a puppy. Not at all. He hasn't been like a puppy for a very long time.

She opens her mouth to say something; she closed it with a pop when she sees how he is sitting. It is a very proper way to sit: upright, back straight and knees slightly knocked together, and his hands over his knees. His posture was exact, rock-hard, and it seemed totally unconscious. Bubblegum knew of the parents that had raised him, and doubted that among their many fine qualities had been lessons in good posture. The stance was identical to her own; she wondered if he was even aware that he was mimicking her. It was possible that he had simply picked it up, or decided to try sitting like that around her.

Bubblegum coughs again; she drives away embarrassment, most of the time, by refocusing. And Finn has already done the same: maybe just because he is not at all good in awkward moments, but she suspects that the city around them troubles him.

To be transparent: it troubles her too.

Buildings rise up like skeletons; hollowed by ancient fires cast down from the heavens in murderous shells, broken and blasted down to the most resilient foundations and supports. These look naked and sad now, worn away by the ages where they haven't been broken down to be reused in new construction. They are remarkably intact; the old human cities that remained in good enough condition to be recognized often grew an unease around anyone who lived near them, tendencies to house genuine monsters instead of superstition notwithstanding.

Bubblegum and Finn look up at the old and dead city spreading for miles, slowly decaying and crumbling into wasteland in the distance. There were no bodies; corpses had long since decayed into the cycle of the world, skeletons long since crumbled, the metal shells of any automatons surviving their makers and going off to their own lives or shut off in suicidal grief. Here and there, something metal glinted where a weapon had been dropped, or a suggestion of rotten residue that might once had been unusually enduring fabric, long ago. Broken glass on the ground, miraculously undisturbed by the years.

Bubblegum and Finn were very different. There was such a gap in their age that their perspectives were as different as a star's and a firefly's. He was solid, resilient, among the last of his kind and well aware of it. She was of a decidedly different state of physical matter than any in Ooo save perhaps the Slime Kingdom's people (And even they had very little in common with her structural matter), and as far as she knew was totally singular. They were different in everything from outlook to species to even basic composition. Even so, they both looked up at this ancient ruin with identical expressions.

Finn eventually looks down at the ground. Bubblegum cannot see his face then, and she turns away when she can see his expression clearly.

He says, not altogether clearly because his throat sounded choked up, "I wish I got to see what places like this looked like... you know. Before."

She doesn't need to ask. She knows.

Because this was a human city. What could have been his home. A place his people had built, had dreamed into thought and given form with things shaped by their hands. Made in the time when 'human' hadn't been almost mythical in Ooo, a reminder of a time when humanity had been strong and lively and reaching ever higher to exceed what those before them had done, a mighty people, doing such grand and great things...

And now it was only a bombed out ruin. With vermin scrabbling to eat in the dark corners of the forgotten buildings, the dust of long-crumbled corpses blowing in the streets and away from here, and now no one knew the city's name or who had lived here or what nation had dwelled over it or even if they had wanted to fight when the bombs fell or not.

If anything, it was a reminder of something she was certain of, terrible though it was. It wasn't something Finn talked about much, and not a thing she liked to think about: she never told him that in almost all her years of existence, he was the only genuine human she had ever met, unmutated or transformed into the first of a new species. Nor that she had heard nothing of any other humans like him in this land, save perhaps Susan and her more mutated kind. That any sort of viable breeding population was so low as to be completely irrelevant.

Finn knew it, and she knew it, and this was the awful thing they didn't want to think about but this city was the perfect reminder of: humanity was dead to the world. Perhaps a few more generations, if that, would remain before they too died out; any descendants, if any could be found at all, would no longer be recognizable as human or most likely even be aware of their ancestors (genealogy not being an easy thing to track in the world).

But humanity was done. For every actual human known to history, you would find at least fifty non-humans: doing great things and making great works, building nations or explaining discoveries, making something new out of the world left to them.

Humanity had birthed Ooo in the fires of their own annihilation. In a sense, they were the parents of all the tribes of Ooo, but this world was their gravestone.

Bubblegum looks up at a hollowed tower: she wonders to herself what it had been for. She imagines that it had once been a place of worship, and fancies what it might have been like. She knows Marceline to cleave to her particular idea of an old world religion her mother had followed, and mentally places the trappings of it over the building. She can't picture it right: she just doesn't know enough, and there is nothing else to tell her what it might have been.

Dust, decay, rot; and then those growing from it. That is humanity's legacy.

She wonders what people were born in this city and left it never knowing what humans might have done to give rise to them.

She catches a similar look in Finn's eyes and says, "They call it 'old world blues'."

Finn gives her a look, almost sharp. "Huh?"

Bubblegum casts her mind back, remembers the phrase from days when survival had been the primary concern of the day and before people had started building their own futures. "It's an expression among people who know a lot about the days before Ooo. Scientists who study the old ways, historians and architects and antiquarians, and-" she pauses, just for a moment. The worlds come out, before she can figure out the best way to assemble them into a form that will hurt the least: "People that know they're dying out."

Finn's face goes carefully blank. Just for a moment, and then expressive again. Almost like something smoothing out and then finding a new shape. It's a little unsettling: she doesn't know what he was thinking or feeling at that moment, and she suspects that he spends time in front of mirrors, practicing how to hide moments like that.

"Um." Finn coughs. "And then?"

She clears her throat. "It's not exactly a out-and-out condition, but some people act like it is. 'Old World Blues', they called it when I was doing stuff like what you do now. Before I built the Candy Kingdom. It's about, huh... when you think a lot about the way the world used to be, about what we used to have before, and what we've all lost, and, uh," she flails a hand about, as if casting around for the right words. "You just get upset and sad over it.

"But worse than that," Bubblegum goes on. "It's an obsession. You think so much about the past, about what's been lost and burned away, that you forget about the now. About the things we can do right away, that we've made and done. And these people, they start to waste away, they lose hope and-"

She stops as Finn looks up at the buildings. Not at the buildings, she realizes after noticing the direction of his gaze. He's looking beyond the buildings, at the sky. There's a troubled look in him, that after a moment resolves into something saddened but firm. "They think so much about the past and what they lost and what they could have had," Finn says then. "That they stop thinking about their future."

"...Yeah," Bubblegum says, and is inwardly ashamed to think that she didn't think he would have realized it so soon.

There is a long moment.

She catches Finn trying not to stare at the buildings and the dust.

Awkwardly, she puts a hand on his shoulder. She thinks about saying something about the strength in diversity, that maybe Ooo is so much stronger because of all the many different people's contributing thoughts that flow on another blood. She thinks about how it might be better for the old things to fade away so something new can come, but even she realizes how heartless that would sound. She thinks about saying that she never had any people of her own and built things beyond what they might have been. She thinks of a dozen other things she used to tell herself and they all sound hollow and meaningless here.

Truth. She thinks about truth.

Nothing comes to mind. Her hand stays on his shoulder.

After a moment, he cautiously reaches up and squeezes her hand. He breathes in, out, and the whole of his body relaxes like a heavy weight came off.