For the ever-so-wonderful Mabel-but-slytherin's birthday! I don't have headcanon discussions, but I do have a oneshot. :'3

Set post-Gravity Falls and anywhere in Supernatural's timeline, honestly.

For Every Lock

May 30, 2017

for mabel-but-slytherin

"Ugh, Mabel, I really don't think—"

"Oh come on, Dipper," Mabel exclaimed, turning around and throwing her hands in the air.

"No, no," he continued, trying to poke his way out from between two hoary branches, fighting through paths his sister had jumped over effortlessly. "I don't think that this is a good—"

She blew raspberries at him.

"I don't think this is a good idea," he panted, finally extricating his ankle from some tangled roots. "Look, I don't think this is the way back to our campground."

"Suuuuure it is," Mabel said.

Her hair looked like a bird's nest, between all of the sticks and leaves poking out of it, but Dipper didn't point this out. She'd only think that it was more reason to stay out here. She'd probably refuse to even enter their tent until a bird graced her hair with its presence.

"No, Mabel," Dipper said, pulling out his compass again. "North is that way," he pointed, "and we've been walking west ever since we crossed that river. We need to head back over to—"

"Oh, where's your sense of adventure, bro-bro?"

"You know," he said, peering between the trees, "you'd think that I'd have lost all sense of adventure when we were twelve and almost destroyed the world. You know, Weirdmaggedon, apocalypses, rifts between dimensions, any of that ring a bell?"

"Pssh," Mabel flapped a hand. "Stop living in the past, Dipper! We're all old and grown up now."

"We're only nineteen, Mabel… still technically teenagers. We can't even legally buy a drink."

"Doesn't stop Grunkle Ford from giving you some every time we visit them."

"That's not the point," Dipper deflected quickly. "Besides, no matter how old we get, I don't think you're ever gonna be grown up."

"You got that right!" Mabel grinned. "Which means that I'm going this way!" she raised her hands into the air and sprinted through the rest of the trees to where the grass began and flopped down on the ground. After extending her arms for full excitement potential, she hurled herself to the side, and began rolling down the hill that Dipper realized they were standing on top of, gaining momentum as she went.

"WHEEEEEEEEEEE!"

"Oh come on," Dipper facepalmed, but as he looked up, he realized that there was a break in the slope and she was headed right for a drop.

He yelled his warning at the same moment Mabel went into freefall.

The tone of her scream didn't change one bit, but then there was a decided thud.

Dipper called out, "Mabel?"

And there was silence.

"Mabel?" he asked, worry filling his voice as he began scrambling down after her. "Mabel!"

He was going as quickly as he could while avoiding the fate of his twin, and realized that he needed to go around either side of the hill in order to avoid the dropoff.

As he rounded the bottom of the hill and came out onto dusty gravel, he found that it wasn't a ditch at all, but a manmade structure built into the hill.

He rushed over to Mabel, who was sitting up and spitting leaves out of her mouth and loudly blowing the hair out of her face.

"Bleh. Brown leaves taste gross," she declared.

"Mabel, are you okay?" Dipper asked, reaching down to help her up.

"Yeah, I'm fine," she said, brushing dirt off of her goldenrod Sasquatch sweater and straightening the skirt over her jeans. "But what was that?" she asked.

"Looks like some kind of air raid shelter? Or a really secure cellar or something…" he looked around, trying to gather clues about the age and purpose of the place from its barren architectural features.

She screeched. "Ahhhhhh, Dipper, it's a little hobbity hole!" she exclaimed, eyes shining in delight. "We have to check it out!"

And she ran up the steps to the metal door only to discover that it was locked.

"Oh, well," Dipper said. "I guess it's time to head back, then." He looked up at the darkening sky and frowned. The sun was already starting to go down and they were easily a few hours away from their campsite, with the way their return trip had gone thus far. He sighed.

"No, we have to go in!" Mabel said, trying to pull open the door while standing in more and more incredulous positions as the seconds passed.

"Uh, no," Dipper countered. "We need to go back to camp. It's already—"

"Well, okay," Mabel said, turning with one hand on her hip. "It's going to be dark soon, right?"

Dipper paused at her sudden switch to seriousness. "Yes?" he asked, almost warily.

"So we probably won't get back to camp tonight anyway, but we need a safe place to spend the night without all of our camping gear. This is our best bet!" she said, brightly.

"What do you mean, this is out best bet? The place is locked.

She tilted her head. "You have the presidential key, dumb-dumb," she said. "Or do you just wear that for show?"

"I—" he stuttered. "What? I mean, yeah, okay, but—"

"But," she said slowly, "it opens any door."

Dipper sputtered. "But I can't just use it to break into places!"

"Dipper," she said, "that's exactly how you're supposed to use it! It unlocks locked doors!"

He glanced at the bunker with its heavy metal door and its dull bricks. "It's probably full of spiders and stuff."

"Spiders are your friends, Dipper!" Mabel said. "They eat all the really icky stuff..."

"Or, it could belong to someone. And we would be trespassing."

"Well, then they would be happy to let two poor lost hungry teenagers take shelter for the night," Mabel argued. "Do it," she urged, striking up a chanting pose. "Presidential key! Presidential key!"

Dipper sighed and reached into his vest to pull the cord out from around his neck. "Fine," he rolled his eyes as Mabel continued chanting.

The key slid into the keyhole. Even after all of these years, Dipper still wasn't sure how it was able to fit into any size lock, but it did, and after a minute of huffing and puffing, it finally turned in the rusty lock, opening it with a click.

The door swung in a few inches and Dipper pushed it open the rest of the way with a creak. He fumbled in his pocket for a flashlight and clicked it on. Mabel followed suit, but outlined smiley faces into the darkness around his steady beam.

It was a large room, and seemed to open up below them, but neither could see much without going inside.

Dipper put one foot over the threshold and looked uneasily back at Mabel. "Are you sure about this?" he asked, still ready to turn around and start the long trek back to their tent.

She shrugged. "I mean we're already here. And it's gonna be a long walk back. Might as well check it out," she said. "They may have beds!"

He shook his head, but didn't feel like arguing the point. So he moved further inside and carefully began picking his way across the floor toward what he thought were some stairs.

He'd only gotten a few feet before the lights flared to life around him. He screamed and dropped his flashlight, which clattered down the stairs.

Mabel was laughing behind him, one of her loud laughs that devolved into snorting, but once he recovered from his fright enough to get a good look around him, he didn't even mind.

The place was huge and well furnished. There were what looked like old WWII-era computer banks and tactical maps, but there was comfortably solid wooden furniture that kept it from looking like a bomb shelter.

And through the large open doorway, he caught sight of shelves and shelves of books—things that he knew would discuss topics that even he had never dreamed of.

His squeal was of delight this time, and he pelted down the stairs without a second thought.

Mabel followed more slowly, and recovered the fall flashlight for him since he was already lost to the library, head turned on its side as he scanned the titles on the spines.

"When Wendigos Walk," he read off. "Ye New Booke of Mynsters, published in 1598? Mabel!" he spazzed.

"Oh look, the Wonderful Wizard of Oz!" she beamed.

"Mabel, Mabel, Mabel!" he said, shaking her by the arm. "This is the coolest. place. ever!"