What's this? Another Mabill fic? But Oilux, you haven't finished writing Let's Make a Deal! And you have that other story, Love Bites.

Well, let me tell you, wonderful reader. This story didn't ask to be written, it demanded it. So here it is. Yay!

Title: All That Glitters Isn't Gold

Pairing: MaBill

Summary/Rating: Things change, nothing stays the same. Mabel realized that when she was fifteen, and Dipper and herself found a stream that changed everything. Things change once more in her life, but most certainly not in the way she was expecting. Monster Falls MaBill AU. Rated T

Chapter 1: There Must Be Something in the Water


In their third summer of Gravity Falls and visiting their great uncle, things change suddenly. It isn't a normal change, one they can take in stride and brush off when they go back home. Simply because with this change there is no going back home. There is no returning to Piedmont, there is no going back to normal. At least, not right away.

Mabel and Dipper were fifteen, walking through the woods when they heard the rush of water. What had originally been a monster hunt had turned into more of a hike, and now as they heard the stream of water, they couldn't help but stop. It was a nice break, one the twins deserved after walking for hours.

The river they thought they heard was more of a stream. Mabel could walk through it and barely get her ankles wet. It's blocked by a dam higher up, as though someone wanted to stop the flow of water. Dipper said the way the stream lead was into town, but Mabel was certain that it doesn't lead there.

"It must come from underground somewhere. I wonder where it starts." Dipper said as he looked over at the small dam, which had formed a puddle. The water always seemed to be coming from somewhere, but Mabel couldn't see where.

"Don't worry about it so much, Dip. You think too much." Mabel laughed, reaching down to splash water at her brother. Dipper sputtered, covering his face. He wasn't quick enough though, and Mabel got him dead on.

"Mabel! What're you, five?" He still put his journal aside, reaching down to splash her back.

"No, I'm six!" She declared, and splashed him again.

The pair erupted in laughter, splashing each other and getting thoroughly soaked with water from the small stream. The water tasted strangely sweet, as though someone added sugar to it. Mabel brushed off the taste, lying on the bank with her brother as they recovered from their water fight.

"Well, this monster hunt was a bust." Her brother declared, standing up, though he swayed in place. "We should get back home before night."

"I don't want to move." Mabel groaned, looking up at the setting sun. Actually, the thought of a nap was wonderful. Mabel never wanted to move from where she was.

Dipper suddenly yawned, laying next to her. "Actually, that does sound pretty great." He mumbled, sitting back heavily on the ground. He laid next to her, sighing happily.

Mabel couldn't keep her eyes open anymore. Her feet still in the water, and with Dipper laying right next to her, she fell asleep.

Waking up with a tail was the strangest thing she had ever experienced. Mabel felt as though her head was stuffed with cotton, her throat dry. She was sure this was what it was like to wake up with a hangover. Mabel groaned, trying to shift, but her lower half was weighed down, and she nearly screamed upon seeing the bright pink tail.

The bottom half of her fin was still submerged in the pond. It's a bright pink, matching her favorite shooting star sweater she was wearing. It glittered in the sunlight, shining and sparkling as though she doused herself in glitter.

"Dipper?" Mabel's voice cracked almost painfully, as she reached out for her brother.

She expected the warm fabric of his vest. She did not expect the feeling of warm fur. Mabel turned her head, sitting up a little as she glanced at him. this time she couldn't hold back the cry from her mouth, and Dipper bolted awake.

"What? What's going on?" Dipper's new hooves scraped against the ground, and his new ears flattened against his head. Mabel couldn't even form words, her mouth opening and closing to make her really look like a fish.

"You have ears!" Mabel finally said, reaching out to touch the soft things. Dipper cringed at first from her touch, but then relaxed.

"You have a tail!" He looked at her brand new tail, reaching out himself to touch it.

It took twenty minutes for them to figure out there must be something in the water. Another twenty minutes for Dipper to figure out how to walk with a completely different set of legs. In that time Mabel discovered she was much like her old romantic interest Mermando, and couldn't come out of the water without suffocating.

Though Dipper doesn't want to, he left her there in the stream, since she couldn't be taken out of it by herself. In the time spent alone waiting for her brother to return, Mabel had fun singing songs to herself and playing skipping the stones in the small pond. Dipper returned with their great uncle, Soos, and the cooler, all on the golf cart to get Mabel out to safety.

Stanley and Stanford take some of the water to investigate, while Soos lifted her into the cooler of water. He tried to make a couple jokes about everything, but Dipper seemed worried beyond belief, and Mabel can't help but feel it's her fault. She was the one who started the splash war. Even though she loves her new tail, she can tell Dipper doesn't enjoy being a deer.

"The lake is where you're going to have to stay, Mabes, until we can get a pool or something." Dipper told her, as Stanley and Stanford tried to find the source of the pool. They seemed to be unearthing something, as more water flowed from it's spot.

Mabel can't find it in her to protest that fact. She has little desire to spend the night alone, but she doesn't want to spend it in the bathtub as well. Stanley and Stanford eventually come back, and they drive Mabel to the lake. Soos picked her cooler up and just dumped her into the water. She laughed and shot around, coming back to the pier.

"Maybe I'll get to see if there's really a Gobblewonker or not." She joked. Though she made a note to avoid it, in case it was hostile.

"You sure you'll be okay out here?" Dipper asked, still unsteady on his legs. Mabel rolled her eyes but nodded.

"I'll be fine, Dip! I'll go find a cave to sleep in." Mabel reassured. "I'll meet you guys here in the morning!"

Though not without a couple of long goodbyes, they finally left, and Mabel was left to her final night alone in the lake. It was a bit scary, being out, but Mabel reassured herself that it was just for a night.

Yet what was meant to be one night quickly turned into two nights. Which quickly turned into a week. Then a week turned into a month, and then a month flew by and summer was over. Dipper came and visited her every day, still a 'cervitaur' as he called it, and told her they still hadn't gotten a cure. That they wouldn't be able to return back to Piedmont.

"What do mom and dad think?" Mabel asked, lying on the sand and soaking up the rays of the sun as Dipper sat next to her and wrote in his journal.

"They're glad we like it here so much." Dipper replied, jotting down another note.

Mabel couldn't think of anything else to say, and dove under the water to bring her brother back a shiny stone. He put it with the others that she had gotten for him, creating a nice little pile.

"Any new leads?" Mabel asked, looking at her hands. She figured one of the good things about being a mermaid was the fact her fingers didn't prune anymore.

Dipper sighed and shook his head, ears twitching. Mabel couldn't think of anything else to say, so she didn't, just resting with her brother and enjoying the company.

One month turned into two, and two into three, until it's the next summer and they're sixteen. They have their birthday party at the lake so Mabel can attend, and Dipper pushed Grunkle Stan into the lake the first chance he got.

The next thing Mabel knew, was more seasons passed as she forgot what it was like to feel the grass between her toes, or what it was like to walk. She discovered her voice could easily put people to sleep when she sang, or that she can't pass up a shiny object without the need to pick it up. The small little cave behind the waterfall quickly becomes full of coins and rocks and everything else she can find. Dipper made fun of her for hoarding, but said he kept everything she gave him.

It's much easier to talk to the creatures of the forest when you're considered one of them. They tell her secrets of the forest they say humans can never know, and made her promise not to tell her family. The creatures whispered how the small stream was now a big river, and the big river was going into the town's water supply. She doesn't breath a word, just as she promised.

Two days after the creatures told her the secret of the water and it's goings, her great uncle Stanley and Stanford came and told her what happened. She doesn't know what's stranger, the fact the creatures were right, or that Stanley is a gargoyle now, and Stanford is a sphynx.

"You're not the only special one now, kiddo!" Stanley grinned, taking off in flight. Stanford just sighed.

"Ignore him, he's so annoying now."

Mabel grinned and laughed, glad she wouldn't have to hide from the townsfolk now that everyone else was just as strange as her and Dipper. She wasn't afraid to swim down the river Gravity Falls had before all this, but now she could do so without hiding from the people.

The creatures whisper other things as well, of a demon who used to roam the woods as a triangle who is now bound to a human body because of the water. The fairies come and visit her in the lake and stop calling him a demon, but call him the hunter instead. They talk about how he's hunting for creatures, to take what he needs from them to gain his original shape once more. It gave Mabel hope though, because if Bill can find a way to change back to normal then so can she and Dipper.

Yet the only thing that remains the same is the fact that things change. Mabel and Dipper are twenty one and haven't seen their parents since they were fifteen. She waited on the bank of the river as she always did, waiting for her daily meeting with her brother. He's running late, and Mabel searched through her small brown bag at the shiny items she had collected that day.

A couple quarters, a seashell, and some shiny rocks. One thing Mabel decided she didn't like early on about being a mermaid was the obsessive need to pick up every shiny thing she saw. Though she supposed it was better than Dipper and his addiction to salt, he said it was from the deer side of him. Mabel doesn't point out how he liked a ridiculous amount of salt before as well.

It's meant to be a normal day. Just like any other, another chapter in the book she calls life. One sound changed everything. As the sound of the gunshot echoed through woods, the mermaid turned and watched her brother come stumbling out of the woods with blood soaking his shirt.