It was an interesting morning in Gravity Falls. The sun was shining, the birds were chirping, everything was peaceful. Stan was up early. He made himself some coffee and read the Gravity Falls Gossiper, only because the TV was broken. "GRUNCLE STAAANNNN!" A voiced cried from the other side of the hallway. Stan looked up from his newspaper and saw two smiling grandchildren eager to tell him news. "Ahh, if it isn't my favorite grandkids!" Stan said, sarcastically. "GRUNCLE STAN, GUESS WHAT TODAY IS!" Mabel yelled with glee. Dipper held out a calendar and shoved it into Stan's face. "IT'S OUR BIRTHDAYS!" Dipper said, excitedly.

"Oh man, really? That's- wait are you two messing with me?" Stan said while staring the two down. Dipper and Mabel shook their heads. " WE'VE BEEN WAITING FOR THIS DAY FOR SO LONG, WHY WOULD WE BE MESSING WITH YOU?!" Mabel, still shouting but in frustration, wondered. Stan's face went from a face of disbelief to a beaming smile. "Well that's great! You know what we should do for your special day?" Stan said while hugging the two rascals. "A PARTYYYY!"

Fast forward a few hours, Dipper and Mabel's party began. The interior of the Mystery Shack was filled with beautiful colored lights, loads of balloons and streamers, and a whole lot of the twins's coolest friends. "Happy Birthday, Dipper!" Wendy said, while holding her gift to the boy who pined for her for a while. Dipper tried so hard not to blush. "Wow, Wendy. Thanks!" He said, with a huge smile on his face. He could not wait to open his presents. "MABEL, HAPPY BIRTHDAY!" Grenda and Candy screamed, while holding two beautifully bedazzled presents. Mabel could not contain her excitement, she grabbed the gifts and hugged her best friends as hard as she could. "YOU GUYS!" Tears streamed down her face. Both twins were filled with pure glee. Stan came out with the twins's birthday cake. It was a vanilla cake decorated cute and pink on one side and had question mark sprinkles on the other, symbolizing the two's unique personalities. "Happy..." Stan started. The guests turned around and notice Stan's cue and began singing along. "...Birthday to you. Happy Birthday to you. Happy Birthday, dear Dipper and Mabel. Happy Birthday to you." The twins looked at each other and smiled. Dipper whispered in Mabel's ear, "Happy Birthday, sis." Mabel smiled at him. They locked eyes for a long time. Then they turned and looked at all of their friends surrounded in the Mystery Shack. Wendy winking at Dipper, Robbie looking angsty but deep down sort of cared, Pacifica doing the same, Grenda and Candy smiling wide, and Stan rubbing his hand behind his neck. He put a lot of work into the cake and was not sure if the two were proud of it, but they were.

"You blow out one side, I'll blow the other." Dipper said to Mabel. They both held their breathes, but Mabel held hers longer. She closed her eyes shut and thought, "I wish we can stay like this forever..." The two blew out their candles. And Mabel woke up.

She opened her eyes. "Yo, Mabs. Class is about to start." A voice said. Mabel opened her eyes. She was in her dorm room. She store blankly at her ceiling. "Dipper..."

Her roommate left because Mabel wouldn't get up. Mabel closed her eyes and dozed off. "Gravity Falls... Dipper... Forever..." She moaned. A sensation arose after she saying those words. "Yes..." She said. Her hand wondered around her body. She began to sweetly masturbate. "Dipper..." She moaned. "Happy Birthday, sis." She remembered from her dream. She tossed and turned, pleasuring herself. Just then, she grabbed a picture of them together from their times in Gravity Falls. "Gra-" She moaned hard. "Gravity..." She thought and thought of all of the memories, she could not contain herself. "FUCK! DIPPER!" She climaxed. She looked at the photograph one last time. "Forever.."