Prompt from Tumblr: Mabel and Dipper go on a monster hunt, and Mabel runs off. When Dipper finds her, something has happened to her as a result of her poking something magic.

Just one minute, she said.

Nothing's gonna happen, Bro Bro, she said.

"Well, if that was true," muttered Dipper, "Then why have I been looking for her for quarter of an hour!"

Dipper ran on, desperate to find his sister. He didn't pay any attention to the way the branches and pine needles scrapped his arm, leaving fine red marks across his skin, nor did he stop when he tripped over an unearthed root. They were on a monster hunt. There were monsters about; he needed to find the sweater clad girl as soon as possible.

It wasn't that he thought Mabel couldn't cope on her own. Well, maybe he did think that, but he had a summer's worth of proof to suggest that, when left to her own devices, Mabel would try and defuse a situation with equal parts love, violence and grappling hook abuse. Generally speaking, that wasn't the best way to deal with the monster of Gravity Falls, Oregon.

Fwoosh

Mabel yelled.

Dipper picked up the pace.

He quickly found a smallish clearing, immediately spotting his sister kneeling near the centre. Floating above her was some kind of giant creature covered in a black smoke. It crackled and seemed to phase in and out of existence around its edges. Even though he wasn't exactly far away, Dipper couldn't tell what it was. It looked somewhat human, but its limbs were impossibly long and skinny.

"Mabel!"

"Dipper!"

Dipper ran towards Mabel while she pointed at the creature.

"Dipper, you won't believe it! I found this adorable little black rabbit and I picked it up and it had this super soft fur and so I just had to poke it. Poke. And then there was this big 'fwoosh'," She splayed her fingers as she mimicked the sound he'd heard earlier, "Sound and then the cute little rabbit became that creepy looking thing over there!"

The creature spat angrily. "I am not adorable and cute, nor am I creepy! I am a púca and I am your worst nightmare!"

Without delay, Dipper grabbed journal 3 from his vest and started flipping through the pages, mumbling 'púca' repeatedly. Apparently unhappy with being ignored in favour of a book, the púca stomped one of its large, talon-tipped foot on the ground. A small rumble followed, and a vine broke free from the ground and whipped haphazardly between the twins.

Mabel dove to the floor to avoid getting slapped whilst Dipper back away, head still in the journal.

"Dipper!" Mabel wailed as she covered her head with her arms.

"I'm trying!" Dipper's voice was just tipping into the realms of being frantic, "The journal doesn't say anything about púcas though!"

The púca laughed, a horrible sound that fluctuated between a deep grumble that fitted its form and a high pitched giggle that wasn't unheard of from a school boy.

"Do you really think some lame book would tell you how to defeat me! You cannot defeat me, puny humans! You can only bow and hope for forgiveness!"

During the púca's speech Mabel had moved to join Dipper, hand tightly clenched to the fabric of his vest. The púca laughed again and crashed its foot into the ground. The vine changed its pattern and shot towards the twins, obviously aiming to slam into their heads and hurt them and

"SEÁN!"

In an instant the vine disappeared. A bemused Dipper and Mabel looked up, only to realise that the púca was no longer in front of them. In fact, it was nowhere to be seen.

"That's my Ma!" Came a timid, Irish voice close to them.

They looked around them for a moment before Mabel squealed. On her shoulder was a little black rabbit. Its eyes were bright with fear and its ears were pressed flush with its back.

"You're a rabbit again!" She squealed.

The púca's, Seán's, nose twitched. Dipper, anticipating another high-pitched noise from his sister, put his hand over Mabel's mouth. It didn't muffle it much

"I can't let my Ma find me. You've gotta help me."

Dipper glared at Seán. It was much easier to do when it wasn't towering over him and emitting some kind of unearthly smoke. "And why should we help you after you tried to attack us?"

"'Cause I'm asking, ya dimwit!" Seán sounded desperate.

"I don't know, man," Dipper started, "Maybe you'd have better luck if you bowed and hoped for forgiveness?"

Seán's ears twitched and his eyes started flicking around. Dipper almost asked about it before he heard the sound of galloping.

"Please! Ya know what? I've seen the jobs that old guy gets ya two to do outside. I'm really good at them and if ya help me I'll do all of ya stinkin' jobs for two weeks!"

Before Dipper or Mabel could answer, the galloping stopped. Three pairs of eyes turned to look at the new arrival to the clearing. A beautiful, sleek black horse stood opposite them. Sunlight that had broken through the dense foliage shone off of its mane, giving it an air of grandeur. It was only amplified through the eyes; both eyes were a glittering gold that swirled around the orbs and it was only Mabel's tugging on his vest that stopped Dipper from getting lost in them.

Mabel's tugging persisted. "There's a basket on her back." He heard her whisper.

Sure enough, where a saddle might be placed on an ordinary horse, for this was certainly not an ordinary horse, was a woven basket, a red cloth covering the top and seemingly balancing without restraints.

Obviously magical black horse wearing a basket that may or may not have something to do with a bratty shapeshifter? Dipper shrugged. It wasn't the weirdest thing he'd seen that summer.

"Seán, you had better not have been upsetting the hikers again." The horse snapped, puffing out air through its flared nostrils. Dipper found himself mildly entranced by watching the horse's mouth form human words.

There was a squeak from Mabel's shoulder, and she seemed to take this as a cue to speak.

"Hiya! You must be Seán's mom. You look really pretty and nothing like Seán!" Mabel grabbed the aforementioned being and held him out in her hands, apparently oblivious to the way the púca lolloped around her palms nervously.

For a brief moment, the horse (Dipper presumed that if she was Seán's mom then she must also be a púca) was taken aback by Mabel's kindly outburst. However, upon seeing the small rabbit in her hands, the púca's golden eyes narrowed.

"I hope my son hasn't done anything to hurt you two."

Seán stopped moving and gave Dipper and Mabel a pleading look, eyes widening significantly.

Mabel reacted instantaneously, flapping the hand that Seán wasn't sat on. "Psh, as if Mrs Awesome Púca-horse! Me and Seán are like besties or something. We were playing a game and Seán was the villain and it was all really cool! If Seán didn't have the amazing shapeshifting trick then my game would have been ruined." She struck a dramatic pose with her free hand to really try and build up sympathy.

The horse-púca seemed to consider the information for a moment. Her tail swished back and forth and Sean seemed to shiver in place on Mabel's flat hand.

"Why didn't ya tell me ya were going to play with friends, ya numpty?"

Seán seemed to deflate as he let out a large, relieved breath. He turned to face his mother.

"Well, Ma, ya were busy baking and I know not to disturb ya when ya baking. Besides, Mabs was already waiting for me and ya always told me it was rude to make people wait." Mabel grinned at the nickname she'd been given.

The horse-púca blinked a few times then let out soft sigh. "I suppose I did, didn't I."

She then trotted towards them, hooves making less sound on the soft ground then when she was running. As she approached, she reached her neck round behind her and grabbed the handle of the basket. She turned back and motioned for Dipper to take it from her.

With her mouth once again free she could speak. "Well, I want you two to have this pie as a present for playing with my Seán this afternoon. If you just leave the basket outside ya house then I'll send Sean to get it tomorrow morning and you can all play again if ya want to." Dipper nodded and clutched the basket closer to him.

The horse-púca turned to look at her son. "And as for you, mister, you can come home right now because supper's almost ready." She lowered her head and Seán leapt from Mabel's hand to his mother's back, transforming into a cat mid-flight to presumably make the jump easier.

His mother looked up again and gave Mabel an affectionate nuzzle. "We'll be seeing ya then, kids. Please look after Sean again in the future."

She turned and started heading out of the clearing back into the deep forest she came from. As they neared the edge, Seán turned back to look at Dipper and Mabel. Mabel waved frantically. Seán could just be seen sticking his tongue out before he disappeared in the darkness of the forest.

After a moment, Mabel piped up. "Seán's mom is so great. I'm so glad we're friends."

"You do know that we're not actually friends with him, right? He literally only went along with that because he didn't want to get in trouble." Dipper replied sardonically.

"But Dipper," She whined, "She gave us a pie!"

"It could be poisoned for all we know. If that Seán guy was so scared of her then think about what she might have done if I'd refused it!"

Mabel gave him a pointed look then removed the red cloth from the basket. In one fluid motion she jabbed her finger through the golden crust and then put it in her mouth. She took a moment to taste the filling before her eyes widened. Suddenly she started coughing and grabbing at her sweater. Dipper panicked and almost dropped the basket when he tried to help her.

As suddenly as she started, she stopped. Mabel peered through a thin veil of hair that had come loose from headband during her coughing fit. She grinned and punched Dipper in the arm, in spite of the worry evident on his face.

"Gotcha Bro Bro! You shoulda seen your face!" She burst out laughing, indifferent to Dipper's stunned look. When she had calmed down enough she gave him a serious look. "By the way, it's apple flavoured. Also, it's starting to get late and I think we need to leave before Stan gets angry."

Dipper sighed. He couldn't stay mad at her for long. "Fine, let's go."

Maybe Stan would be appeased by the sight of an apple pie.

oO-0-Oo

This was super fun to write, and I'd forgotten how much I liked Púcas until I thought about using them for this.