"No, Mabel! You've got a whole bag, what do you need to use part of mine for?"
"These bags aren't big enough!" Mabel exclaimed. "I need enough room for all my things until Christmas!"
Dipper groaned in frustration as Mabel shouldered her way past him to stuff a pile of sweaters into the large empty space in his duffel bag. He had been planning on packing a few novels in there. "There's no room for my things now," he complained.
"You don't need room, Dipper," Mabel stated as if it should have been obvious. "You've been wearing the same thing since you were twelve years old!"
Dipper was about to protest—he had grown a few sizes since then, at least—but Mabel had already raced across the room to gather up her paints, which she did manage to fit in a side pocket of her own bag.
It was early September: the twins' parents had taken them on a cruise to celebrate both their high school graduation and their eighteenth birthday. A far better present, however (to and from each other), was their extended trip to Gravity Falls. Their parents wanted them home for Christmas, and Dipper figured that was only fair.
"You said the bus comes at one, right?" Dipper asked conversationally, trying to wedge his books between the folds of Mabel's sweaters.
"No way, Dipstick, I said twelve thirty-one," Mabel replied, swinging her feet off the bed as she watched her brother struggle. "I think you packed too much."
"I didn't," Dipper retorted, and then straightened up abruptly. "Wait: twelve-thirty?" He glanced at the clock in alarm. "It's almost twelve now!"
"Guess we better hurry then, huh?" Mabel giggled, hopping off the bed and shouldering her bag.
"This would be a lot easier if you had agreed to ask mom and dad for a car," Dipper grumbled as he hastily zipped his bag up and stood. Both twins headed for the door, bickering all the way there.
"I can't even drive! Why would I want a car?"
"Oh come on, you can learn to drive!"
"But neither of us had to learn anything to take a relaxing cruise. And that was good for both of us."
Dipper rolled his eyes as they emerged onto the sidewalk. He had not enjoyed the trip nearly as much as Mabel had, but she was right in saying it was more universally suitable.
Running as fast as they could while encumbered with four months' worth of belongings, the twins made it to the bus station with four minutes to spare, but they were still forced to dash from the ticket desk to the platform. There were only three other people on the bus, so neither storage nor seats were an issue.
"Gravity Falls, here we come!" Mabel cheered, thrusting her fists into the air and drawing strange looks from the other passengers.
Dipper was excited too. The twins had gone back to the Mystery Shack for the last four summers, and he was looking forward to seeing everyone once again. Soos had fixed the place up well: the windows and doors had been replaced; the lettering on the roof had been fixed and repainted; a proper pen had been built for both Gompers and Waddles, who was sent back to Oregon by the twins' parents; the grounds had been cleaned up; and the basement had been opened up. Dipper had helped with this last task, archiving Ford's projects and determining which were safe enough to be shown as exhibits. The Mystery Shack now housed actual mysteries, a fact of which everyone involved was proud.
The bus ride was shorter than Dipper remembered, because his mind was racing. Not only was he trying to concentrate on the thousands of ideas running through his mind, but Mabel was characteristically chatting his ear off. A game of Bus Seat Scavenger Hunt took up the latter part of the trip, but they only made a few stops anyways. By the time they got to Gravity Falls, Dipper and Mabel were the only people left on the bus.
The driver seemed anxious to leave again, and the twins had barely lugged their bags out from the cubbies under the bus before it was peeling off in a puff of smoke. Grinning nonetheless, the twins turned towards the Shack and dragged their bags there in their eagerness to arrive.
Mabel threw the door open. "MABEL is here!" she announced. "And Dipper!"
Soos, tidying up a rack of t-shirts, did not seem surprised to see them, though he rarely seemed surprised at anything. "Oh. Hey dudes," he greeted.
"Yoooo, Dipper," Wendy said from behind the counter. "Thought you weren't coming back this year."
"Are you kidding?" Dipper chuckled. "I wouldn't miss this for the world."
Mabel planted her hands on her hips. "And you're stuck with us until Christmas this year!" she asserted. "Dipper and I are grown-ups now, and out of school too!"
"Cool beans, lil' dudes," Soos said, bobbing his head amiably. "Oh. Wait. Does that mean you want different rooms now?"
Both twins drew in a breath to enthusiastically affirm the question, but they caught each other's eyes and everything that had ever transpired in that room suddenly passed between them.
"Nah, it's okay," said Dipper, and Mabel nodded her agreement. "Better go put this stuff upstairs."
Dipper sank onto his bed gratefully while Mabel threw herself backwards onto hers. "It's great to be back," she sighed. "Hey, those star stickers are still on the ceiling. Do you think they—WADDLES!" Suddenly remembering her porcine friend, Mabel darted out the door and down the stairs faster than Dipper could blink.
Dipper kicked his shoes off and laid back, his eyes roving the contours of the familiar room. He inhaled deeply; it even smelled like home. His pleasant reverie was interrupted by a commotion form downstairs: the door opening, some shuffling, what sounded like a scream…? Dipper rolled off the bed and crept down the stairs carefully.
Wendy, Soos, and Mabel appeared to all be surrounding a figure in the doorway, talking all at once and huddled together. There was an inarticulate roar of irritation and the figure freed itself from the embrace.
"Come on! Walk in the door and I get mauled. What are you guys, some sort of booby-trapped human alarm system?" He grinned and snapped his fingers. "Human Alarm System! I can sell that!"
Dipper jumped the last few steps to join the others. "Grunkle Stan!" he exclaimed, even while trying to look around him. "But wait…that means—Great Uncle Ford!" He swerved around the group to launch himself at the other figure coming through the doorway.
"Dipper!" Ford laughed, giving the younger man a quick one-armed hug. "And Mabel! I didn't expect to see you two here."
"Welcome back, Great Uncle Ford," said Mabel, taking her turn to hug him. "Hey! This is great! We're all here at once!"
"Great, yeah…" muttered Stan, who was secretly pleased. "Hey! What'd you do to my Shack?" he demanded of Soos.
"Oh, I fixed it up a bit, Mr. Pines," Soos told him, then adding quickly: "But don't worry, I didn't touch your room."
Mabel had grabbed Dipper by the shoulders and was shaking him. "Can you believe this, bro-bro? This is gonna be the best four months ever!"