Monster Falls – Always and Forever
Once upon a time, Mabel Pines had loved unicorns, with the obsessive love of a twelve year old who also deeply loved pink, glitter, and kittens.
The love of pink, glitter, and kittens remained, but the love of unicorns died a tragic and fiery death a little while after her Grunkle Ford returned home, when she had to go on an epic quest for unicorn hair to protect their home and she found out just what kind of jerks the unicorns of Gravity Falls were.
Which was probably one of the many reasons why, when the Fluventis hit, she found herself dealing with four legs and a horn even as her brother tried to deal with his own new found set of four legs.
She was just grateful that, so far, her transformation didn't come with too many new instincts. Watching her brother deal with suddenly finding himself literally frozen in the face of danger was hard enough to watch without having to deal with it herself.
Still, they coped. They learned – slowly, and with a lot of fumbling, missteps, and teasing – to walk on their new limbs, how to run or sprint, how to use the new powers that came with suddenly being a monster.
The rest of the town was patient with them, as they were all dealing with roughly the same things. At least, they were patient once the fear and panic was over, and they stopped trying to point fingers or figure out who was to blame.
For most of them, it was a little hard to hold a grudge when the people who might have caused it were dealing with the consequences the same as you were, and it had come from trying to help, and were working themselves to the bone to fix it.
Well, mostly they were trying to help. It was hard to tell with Stan sometimes.
Bill Cipher had been quiet ever since the Fluventis had hit, and Ford theorized that he either couldn't get through to their dreams while everyone was a monster, or it had somehow messed up his plans enough that he was laying low until he could figure out how to deal with it all.
That, or he somehow was physical just long enough to get hit with it too, but that was highly unlikely. They could wish, but unlikely.
But in town, it seemed no one had escaped unscathed from the Fluventis, and that was enough to distract them from wondering about a dream demon's plans.
Ford may not have liked the Mystery Shack, but he'd gotten used to it, tolerated it, even grown slightly amused by it. After the Fluventus (and his brother turning into a gargoyle, a creature that could sense lies, and himself morphing into a sphinx – a miscalculation, believing he'd be able to change back and finding himself as trapped as the rest of the town – and able to demand the truth, forcing them into a conversation neither brother had really been ready for) he actually had to admit that he was glad Stan had made it.
Because, thanks to Mabel's quick hands and clever crafting mind, they had zippers and strings, slats and buttons and makeup that made their creature forms into costumes, disguises that mimicked poor ones at that. Tourists would turn away from things that were too real, but the zippers that peeked out, the strings and buttons, convinced them all that it was all a show, and Mabel gave them out to everyone.
The entire town depended on forestry and tourism, and with so many of them connected to the forest now, depending on its health to live, they had to turn entirely to the busloads of tourists – and their new 'costumes' were bringing them in higher numbers than ever before.
Dealing with the tourists was easier than dealing with the twin's parents. Because they had to be told something when it became obvious this wasn't going to just go away, and they weren't going to find a cure before the end of summer.
This was one time Grunkle Stan's lies failed. Ford's apprenticeship wasn't even enough to convince them that the twins should stay, and it was difficult to convey "Your kids can't even get on a bus right now" without panicking them.
Them making the decision to come up to Gravity Falls to see just what was going on was simultaneously awkward and terrifying.
To say the twin's parents panicked when they arrived and saw their children, found out about the Fluventis and what had happened to the town, would be downplaying the situation.
Soon after their arrival, the adults had retired to the kitchen to talk things over, though with the kids' now improved hearing it hadn't really helped.
Dipper disappeared into the woods after the first two hours of arguing. As one of the very few prey creatures in the Falls, he was having a harder and harder time of dealing with arguments and confrontation.
(Grunkle Ford, who had some experience in the woods from before the portal, tried to help by telling stories of how aggressive adult deer could be, how strong they were if you messed with them. It was little comfort, since Dipper would have to grow up a cervitaur for it to matter. Dipper was just mature enough to recognize the attempt at helping, not mature enough for it to help.)
After another hour, Mabel went to find him. She was still getting used to being half unicorn, but one perk so far was being able to move easily and near silently through the forest. She was having a hard time listening to the argument in the Shack, and she was worried now for Dipper.
She still wasn't as good at being quiet and hidden as her brother, especially when he sat down and didn't move, his spots hiding him from nearly everyone. Which meant that finding him was going to take some time.
Mabel eventually found Dipper in the small clearing they had partially claimed as their thinking spot earlier that summer, sitting and staring at the waving grass.
Stiffly, though with more confidence than she'd had when she'd first transformed, Mabel lowered herself to sit beside her brother.
He leaned into her side and she leaned back, mutual comfort and support. They sat like that in silence for a time, not saying anything, just sitting.
"Nobody blames you for this," Mabel said finally. "You know that, right, bro?"
"...if Great Uncle Ford and I hadn't been messing around in the forest, no one would have gotten infected," Dipper countered.
"It looked like normal water," Mabel argued back, horn giving off little sparks with irritation and tail lashing. "We even boiled it to make sure it was safe. We tried. Or are you going to blame yourself for the drought that made us look for water in the first place, too?" she half teased, elbowing her brother in the side.
"Mabel..." he groaned, shoving back, but he was smiling now, so she grinned back.
"Dip-per," she mimicked, leaning against him again. He huffed but shifted so they were pressed together more than before. "It could've been worse, bro-bro. Think about it. I mean, we could've gotten shoved into like, an air monster and a water monster. Like...like a sphinx and a mermaid! At least we're still this close. Though come to think of it, being a mermaid could be cool..."
Dipper shuddered. "Yeah, but then we wouldn't get to hang out anymore," he said softly. "Or you'd be stuck in a tank all the time, if you wanted to stay with us."
Mabel grimaced. "Oh. Yeah. See, bright side!"
Dipper grimaced, but it was more smile than actual irritation. "Mabel, that's not how that works."
"It is now. C'mon, Dipdop, you can't say you haven't had some fun learning how to be half deer," Mabel said, "and at least we're still together. ...Mystery Twins?" she offered her fist for a bump, since a hug would be awkward with how they were sitting, unable to twist far enough for an awkward sibling hug.
"...Mystery Twins," he agreed after a second, returning the bump. "You ready to head back in?"
"...nah. I like it out here. Just me and you."
"...yeah. Just me and you," Dipper agreed softly, his arm going around her shoulders while hers found its way around his waist. "Now and forever."
So long as they were together, they could face this.
(It took the adults hours to come to a conclusion, but in the end, the Pines parents went back to Piedmont and left their children in Gravity Falls. They had wanted to stay, but all four Pines just disappearing, moving to Gravity Falls on the spur of the moment...that was going to draw attention.
Later, perhaps, they could move to Gravity Falls, if it looked like there was no cure. Maybe they would even take the Fluventus themselves, or stay human to be a lifeline for the town to the outside world. But that was in the future, and until then, they would cover for the twins, and help from afar as best they could.
But for now, they all had each other, even if it was separated by distance. And that was how it always had been, and always would be.)
(A/N: I made Mabel a unicorn in this fic so I could have the scene with them in a field. I like MerMabel, but that scene was the first thing that came to mind with this AU and this prompt, so...)