Wednesday, August 31, 2016. 8:30 AM. Piedmont, California.

Mabel walked down the stairs into the living room to find her father putting on his necktie.

"I thought you were taking the day off today," Mabel brought up. "You said you were going to stay home just so you could celebrate me and Dipper's birthday."

Mr. Pines let out a sigh. "I know, sweetie. But my department has a short-notice and urgent task I must attend to. Being a boss is not as glorious as one would think."

Mabel put up a face of pity and wrapped herself around her dad from his side.

"That sucks so much. I was really looking forward to some father-children bonding," Mabel mumbled.

Mr. Pines repositioned himself so Mabel is instead hugging him from his front. "I was too. But I promise to be back this evening to see you and Dipper blow out your birthday candles. That I can guarantee."

Mabel made a muffled sound, which Mr. Pines could not make out as Mabel's face is pressed against his chest. Mr. Pines let out a chuckle.

"Look at you. You and Dipper are now seventeen. Time flies by so quickly," Mr. Pines said nostalgically. "One day you two are infants, and the next day you two are almost done with high school. I would see you and your brother standing in blue gowns on stage before I even know it."

"Yeah. I'm really looking forward to graduation," Mabel said. She pulled her face away from her dad's suit. "Finally, I am a real woman now."

"My little girl is all grown up," Mr. Pines commented, and he kissed Mabel's forehead. Mabel let out a small chuckle, and detached herself from her father. Mr. Pines picked up his coat and briefcase and headed towards the garage.

"Be safe while driving," Mabel reminded. "I love you."

"I love you, too. And Happy Birthday. Tell Dipper I bid that to him as well."

"I will," Mabel smiled. "Bye."

As Mabel walked back upstairs to her room, she could hear the garage door opening, indicating her father's to-be departure all the way down to San José.

Mabel entered her bedroom to find the family cat on her chair playing with a ball of yarn. Waddles is still curled up on his cushion sound asleep, and doesn't seem to be bothered by the purring the cat is making.

The cat looked up at Mabel upon hearing her enter. Knowing that one of its masters has returned and would like to have her space back, the cat stood upright, jumped off the chair and sped walk passed Mabel into the hallway. Waddles let out a small snort, rolled over on his cushion, and returned to snoring.

Mabel picked up the ball of yarn and placed it back onto her pile of unfinished sweaters. She slumped into her swivel chair and lazily spun around a few times. She let out a sigh and rubbed her face with her hands.

"Ugh, school starts tomorrow," Mabel groaned out loud. "Why must our birthday always fall on the last day of summer, if not on the first day of school?"

Mabel dropped her hands onto her thighs. She slowly spun around a couple more times before catching sight of her most recent yearbook on her desk scattered with AP bulletins and college pamphlets.

Mabel rolled her chair towards her desk and picked up her yearbook. She randomly flipped through the pages, not really taking much effort in absorbing the various pictures and colorful designs spread across the book. However, upon reaching one of the back signature pages, something caught Mabel's attention.

Mabel flipped back to the mostly-blank signature page that has a single message written on it in silver ink. The color almost matched the whiteness of the paper; no wonder Mabel has never seen that message before. Besides, she doesn't even remember this person signing her yearbook.

"Hey Mabel, if there is one thing I should say to you, it is these two words: grow up! I mean, come on, what kind of sixteen-year-old still eats candy and believes in unicorns?" the message said. "To be honest, I'm trying to help you here. You're almost nearing college, and one thing real grown women do not tolerate is complete silliness or nonsense. – Holly Sandoval."

Okay, that was hurtful, Mabel thought. However, almost instantly, Mabel realized that the message, although blunt, actually holds some truth. Come to think of it, she still acts like a kindergarten girl. Mabel still watches those toddler shows that air on Disney Junior, occasionally eats glitter, and knit sweaters with obvious little kid meanings on them, like hearts, rainbows, butterflies, and bunnies.

Mabel leaned back on her swivel chair, and gazed at the many boy band posters she has pasted on the walls. She isn't really obsessed over any of them anymore, but she still listens to their songs very frequently.

Mabel then shifted her gaze back onto her desk. Her eyes landed on a picture frame containing a photo of her beside a lady dressed up as Rapunzel at Shanghai Disneyland's Enchanted Storybook Castle. For the summer of 2016, Mabel and her family had visited Shanghai, Nanjing, and Hangzhou, and stopped by the world's newest Disneyland Resort the day before they were to fly back home. Mabel had a blast, and felt that going to the park was a great way to end her 8-to-11 day vacation. As Mabel recalled, she doesn't remember seeing a lot of teenagers in the park; most of the youngsters seem to below twelve years of age.

Mabel again grabbed her yearbook and flipped back to the glaring message. She read through it multiple times before sighing and closing the yearbook. Holly Sandoval is right – Mabel is just too childish.

Sure, Mabel may have already gone through the whole silliness self-awareness ordeal, but that was when she and Dipper were twelve; they were still more than two months away from being "technically teenagers." But now Mabel and Dipper are seventeen – only one year away before they would be considered legal adults. The age matters. And at her age, she shouldn't even be doing, let alone show interest, in any of those childish things that she started doing long before elementary school anymore. It's time for her to put down the knitting tools and stop sticking her hands into the jelly bean jar. It's time to discard the pink confetti ribbons and store the crayons meant for preschool artists.

"Good morning, Mabel," a voice suddenly interrupted Mabel's thoughts.

Mabel turned towards her bedroom door to find her brother standing there. He made a yawn before proceeding to enter the room.

"Good morning, Dipper," Mabel replied. She tried to sound cheerful, but couldn't get herself to. It didn't take long for Dipper to find out that something is wrong.

"Hey, are you alright?" Dipper asked. He placed his hand on Mabel's shoulder. "Come on, Mabel. Today's our birthday. You should be happy."

"I know, but it's just that..," Mabel paused and let out a sigh. "It's complicated."

"I feel you. We may be seventeen today, but that doesn't mean our hormones aren't attacking anymore," Dipper commented. "Even I don't recognize myself sometimes."

"Yeah. I guess it's just that," Mabel responded, though a large part of her doubts it. "Still, I'm just…not really in the right mood."

"Is something bothering you?" Dipper suggested. "Would you like to talk about it?"

Mabel made a whimper noise and shook her head. Dipper turned Mabel's chair so that she is facing him. Mabel looked up at Dipper's caring eyes, which relaxed her to some extent, but she otherwise still feels depressed.

Dipper lowered himself slightly and kissed Mabel on the forehead. Mabel immediately felt better; whenever Dipper kisses her forehead, any negative feelings she has goes away almost instantly.

"Maybe you will feel better after having breakfast," Dipper said. "Come on. Why don't you drink some of your Mabel-juice?"

Mabel broke a laugh-like smile at Dipper mentioning one of her most favorite recipes. Mabel got up and put her arm around her brother as the two left the room to eat.

2:45 PM.

Mabel is sitting on the living room couch idling. As much as she is aware that it is the last day of summer, she cannot help but feel bored. She doesn't know what she could do to seize the day while it lasts.

Mabel spotted a small travel map of Oakland on the side table next to the couch. Mabel grabbed it, and opened it up. She spotted the publication year as 2003.

This thing is most certainly outdated. Why do we even have this still? Mabel thought. She laid the map onto her lap and started folding it, as if she is making origami. Within a minute, Mabel folded the map into a paper hat. Mabel put the hat on and took out her phone to take a selfie.

However, upon seeing herself in the selfie mode on her smartphone screen, Mabel immediately remembered the thoughts that were troubling her that morning. Shortly after breakfast, Mabel had forgotten about worrying over her childish and silly self. Now that Mabel can see how goofy she looks with that paper hat on her screen, she cannot help but return to that earlier self-conscious state.

Mabel let out a sigh and put down her phone. She took off the paper hat and stared at it. Once when she made a paper hat out of some random cipher document, she managed to create a map that later helped her and Dipper crack one of the biggest mysteries behind Gravity Falls. But in the current case, what's funny is that what Mabel used to create this hat is already a map.

"Ugh, what is wrong with me?" Mabel moaned. She set the hat onto the couch-side table. Mabel again rubbed her face with her hands.

"I like being silly and all…it reminds me of being a kid," Mabel sighed. "But now that I am seventeen years old, is it even necessary for me to keep acting this way? Now that I think of it, acting like a little girl or being all stupid would probably be detrimental when I go out to the real world. I don't know how, but I just know."

"What are you talking about?" Dipper's voice suddenly came out.

Mabel snapped herself back to reality and saw Dipper approaching her. He sat down on the couch beside his sister.

"You were mumbling to yourself," Dipper pointed out. "Are you sure you don't want to tell me what is bothering you?"

Mabel shook her head like a first-grader refusing to eat her vegetables. As much as she wants to confide in Dipper, she feels embarrassed even talking about it.

"Mabel, please," Dipper continued, with deep care in his voice. "You were not yourself since this morning. Usually even on the gloomiest days you still maintain a positive and hyper attitude."

Mabel only let out a whimper. Dipper took Mabel's hand, and squeezed it.

"Seriously, Mabel. I want to know what is troubling you. Your lack of silliness today is starting to worry me," Dipper admitted.

"Silliness?" Mabel finally spoke. "You actually want my silliness?"

"What do you mean?"

Mabel let out yet another sigh. Better to get her concerns off her back. Besides, Dipper is a compassionate person – especially towards his sister.

"Okay, Dipper, here's the thing," Mabel started. "I'm starting to feel guilty about my silly self again. I know I've already gone through this already, but – that was when we were younger, and being silly was still acceptable. But now that we are seventeen today, I'm starting to have second thoughts about acting like a kid again."

"Aw, Mabel. Being silly is nothing to be ashamed of. It's what makes you, well, you. Without it, who will you be?"

"You're just saying that. I know being silly and childish is what makes me who I am. But at this age and time, is that even a good individual personality? I mean, we're going to college soon, Dipper. College is a serious institution. No one on campus would tolerate a grown woman who still eats ice cream for dinner. In fact, they'd probably be wondering how a third-grader managed to get accepted by the admissions team."

"That worry is too out of this world," Dipper reassured. "Universities don't care about whether you are silly during your free time or not. In fact, I'd say that always having a positive outlook even during the worst or serious situations is something most admission teams would be impressed by."

"You really think so?" Mabel continued to doubt.

"Of course. Your personality is a fun one, Mabel. I'm very sure many colleges would like to have you attend their school to add to the student diversity. Everyone is unique, and acting like a child or being all goofy is a special aspect of you. You should be proud of that."

"Thanks, Dipper," Mabel said. She huddled closer to her brother. Dipper put his arm around Mabel.

"But Dipper…," Mabel proceeded. "Well…how should I say this? Okay…you don't think being silly is a sign of immaturity?"

"Of course not, Mabel," Dipper responded. "You are not immature in any way."

"But a lot of teens our age might say so," Mabel sighed. "That's what I'm worried about." Mabel let out another whimper. "I may have friends, but that doesn't mean I'm still scorned upon by most people as if I'm not even human. It really hurts just to think about that."

"Hey, you remember the times when I go through a period of low self-esteem or constant self-doubt? How I always groan about how people hate me and how I have no friends and junk?" Dipper reminded. "You were the one who told me not to care about what they think. You constantly reassure me that there is nothing wrong with me being all 'nerdy' or 'mathematical.' My insecurity often gets me really badly – but Mabel, with your true social intelligence and optimistic attitude, you managed to convince me that I am perfect the way I am."

"Perhaps. But being a serious, study-loving geek is actually quite common," Mabel moaned. "There has bound to be thousands of people like you out there – it's one of the most common teenage phenomena. Being the exact opposite – a silly toddler that still enjoys reading those cheesy princess-marry-prince stories – is rarer, I am sure."

"Come on, Mabel. If you know that weirdos like me are common, then that means you should know just as well that fun-loving people like you are just as widespread," Dipper reassured. "Our school just happens to be a very academic-oriented one, and no one really has time to slow down and reminisce on how it was like to be younger. But despite the constant workload we have been given these past three years, you've managed to remain yourself – your hyperactive, cartoon-loving self. And I'm saying this in a good way."

"Speaking of cartoons…it's okay to watch those classical animated Disney films retelling those prince-and-princess storybook tales, right, at my age? You do know that the main audience of those films is little kids. I don't think I qualify to be in that audience anymore."

"That's not really the case, Mabel," Dipper replied. "Let's not forget that those in who were in charge of the production of those so-called 'kiddie' Disney films were grown men. The films just happen to appeal to the young audience. But really, the films were made so that people of any age, any gender can watch and enjoy them. So when the next Disney animated film comes out, don't feel embarrassed or anything on wanting to go see it. Besides, the heroine in the upcoming one isn't going to have a love interest anyways. That means there won't be any 'cheesy' romance typical of many other Disney films."

"Yeah. Not to mention that a big wresting guy has done the main male voice," Mabel brought up.

"Don't forget that the one voicing the heroine is only 15 years old," Dipper added. "She's younger than us and is already playing the lead role for the next Disney film, which I'm sure is going to be a success, just like those other ones. To be honest, actually, I'm kind of looking forward to the film myself. Hey, tell you what: when that movie comes out in November, let's go to the theater and watch it together, just like when all those other Disney films came out in the past. Think of it as a treat from me. I'll pay for the tickets and popcorn."

"Thanks, Dipper," Mabel said. "You're the best brother ever."

"But getting back to the point, Mabel," Dipper continued. "There is nothing wrong with you staying your goofy or childish self. You like being a kid, and that's okay – good, actually. In the past I was looking forward to growing up, but now I know that being an adult is not as glamorous as I once thought."

"Yeah. I mean, even dad had to get his personal choice on taking the day off today revoked."

"That's the reality of being an adult. Childhood is short – and I'll admit that I'm still learning that – and we must cherish it. So if you want to make yourself feel like a kid for as long as possible, go for it. Watch some old cartoons for old times' sake. Go to the park and pick some flowers. It's all up to you."

"Thanks, Dipper. I guess I was just overthinking again," Mabel said, and then added, with some humor, "I guess it really is just my hormones."

Dipper made a small chuckle, and he wrapped both his arms around Mabel. Mabel curled up into a ball and further pressed herself against Dipper's vest.

"Mabel, just remember that, at least to me, you will always be my fun-loving, goofy, optimistic sister," Dipper whispered. "You are perfect the way you are, Mabel, and I love you for that. Don't ever change yourself just because others think you are immature."

"Thank you, bro-bro," Mabel responded.

"I love you," Dipper replied softly.

"I love you too," Mabel whispered.

Dipper stroked Mabel's hair as Mabel purred like a cat in his loving embrace. Dipper then lowered his head and kissed Mabel's forehead. Mabel smiled, and closed her eyes as she cherishes her brother's warmth.

The two continue to hug each other for the next minute. Then the sound of the garage door opening caught Mabel's attention.

"Dad's home!" Mabel detached from Dipper and sprung up from the couch. "He's back, just like he promised! I hope he brought back presents for us!"

Mabel ran to the garage to greet her dad, in a similar manner as an enthusiastic little girl running to meet her airline pilot-father. Dipper just chuckled, and also got up to follow his sister.

9:50 PM.

Mabel zipped up her backup and placed it next to her bedroom door. She then, one by one, put the textbooks she will need throughout the school year into a separate bag, and also placed it next to the doorway.

After getting ready the supplies needed for school, Mabel went over to her sweater pile. She leafed through it for a brief moment, and picked out a sweater she has just finished knitting earlier that week – it is white with a yellow, cartoon-like pencil with a red eraser attached to it. A black strip of graphite trailed behind the pointy tip. Mabel decided that this is what she will wear tomorrow – it fits the back-to-school spirit very well.

Mabel strolled over to her bookshelf and took out one of the earliest scrapbooks she has compiled. She plopped down onto her bed and started looking through the old memories from preschool and kindergarten.

After flipping a few pages, Mabel came across a picture of her and Dipper, about four or five years old at the time, snuggled together under a blanket on the couch, sleeping. Mabel laughed as she saw in pink pen ink the word "AWWW" in her old elementary-school handwriting with an arrow pointing to the picture.

"Ah, memories," Mabel commented. She was about to flip to the next page when an idea crossed her mind.

Mabel put down the scrapbook onto her bedside table, grabbed her pillow, shut off the lights and went out of her room. She entered Dipper's room to find him reading one of his mystery novels.

"Hey Dipper," Mabel called out. "Is it okay if I sleep with you tonight?"

Dipper looked up from his book, and smiled at his sister. "Of course, Mabel. But, just out of curiosity - does this have anything to do with…well…being a kid?"

"Yeah," Mabel admitted. "I remember when we were little whenever one of us was scared we would sleep together. It was really cute."

"I remember that too," Dipper said. "We still do that now, actually, even if not as much as in the past."

"Well, like what you said, there is nothing wrong with trying to feel like a kid as long as possible."

Dipper scooted his pillow over so Mabel can place hers in the open space. Mabel climbed onto the bed beside him and crawled under the covers.

Dipper put his book onto his bedside table and turned off his lamp. Mabel clutched Dipper's shirt as she curled up into a ball underneath the blankets.

"I love you, Dipper," Mabel muffled.

"I love you too, Mabel," Dipper said as he strokes his sister's hair. "Good night."

"Good night. Happy Birthday."

"Happy Birthday to you, too."

Dipper closed his eyes to go to sleep. While it is Mabel to fall asleep first, clinging onto Dipper, her brother after drifting off also slowly reciprocated the hug. For the remainder of the night, the twins slept peacefully, holding each other in a cozy huddle in the final hours of their last childhood summer.

Gravity Falls was created by Alex Hirsch and produced by Disney Television Animation. All characters and related media belong to Disney.

Piedmont High School is an actual school in Piedmont, California. Its 2016-2017 academic year actually started on Tuesday, August 16, 2016, about two weeks earlier than September 1.

Moana, released November 23, 2016, and Tangled are produced by Walt Disney Animation Studios. Auli'i Cravalho and Dwayne Johnson star as the main roles in Moana.