Note
Like I said, this isn't canon, and is just here for people like that one guest, who seems to be having a rough time with the story. Also because posting it will make more people notice this story (PS: that's the main reason!).
Dipper and Mabel looked at their Great Uncle's computer screen, horrified at what they had just read. Mabel threw up into a trash can. Dipper was going to, too, but he didn't want to puke on his sister's head. When she was finally done emptying the contents of her stomach, she sat up and asked to her twin brother "Dipper, what the fuck did I just read?", probably traumatized for life. "I have no clue, but it was twisted." Dipper responded. "Grunkle Stan would never do that. And who the hell is writing stories about us?" He followed up. "Creepy. This depravity falls stuff is cuckoo." Mabel added before she decided she would go downstairs for snacks to refill her emptied out stomach. Dipper decided to go back to his room, and begin deciphering things his great uncle Stanford had written into the new Journal #4. Grunkle Stan, however, downstairs, restocking the gift shop while Mabel ate, was bored as shit. He needed some excitement in his life. Just then, however, he had an idea. He grabbed a cheap plastic globe, and got in the golf cart, driving into the deep forest.
After about half an hour of this idle Trying-to-forget-the-fucking-awful-story-I-just-read activity, Grunkle Stan had returned. He went up to the attic, where his great nephew was reading. Grunkle stan burst in. "Grunkle Stan! You messed up my train of thought!" Dipper said in an angry tone. "Yeah yeah yeah." The Grunkle replied. "I have something really cool I wanna show ya, and it looks like it will be just me and you because Mabel is stuffing her face with Cheeze Balls." Grunkle Stan said. Dipper forgot his anger pretty much instantly, the thought of exploring the woods with Grunkle Stan and finding new secrets of Gravity Falls made him happy, and he jumped up off his bed and onto the floor. "What is it Grunkle Stan?!" Dipper yelled excitedly. "Follow me kid. I found something in the deep woods." replied the wrinkly man. As Mabel saw them leaving, she asked them where they were going. "Grunkle Stan is taking me into the deep woods to explore!" Dipper said enthusiastically. Mabel insisted that she wanted to come with, much to the excitement of her Great Uncle. Double fun… he thought.
Mabel, Dipper and Grunkle Stan were walking through woods, and had been for fucking ever. "Grunkle Stan, we-were really deep in the woods, what were you doing out here?" Dipper said suspiciously. "Collecting firewood, there's lotsa dead trees out here." replied Stan. "Ok
Dipper replied, stupid enough to believe that. "Wow, it's pretty dark in here…" Mabel thought out loud. Eventually they came across a small clearing with a single stump in the middle and an axe in one of the surrounding trees. On the stump was a Crystal Ball. However, it was a cheap plastic piece of crap, only there to distract the twins. "Woah! What do you think it is Grunkle stan?" said Dipper inspecting the fake ball as Stan the Man had planned. "I dunno, that's why I brought you here." explained Stan. Mabel's heart suddenly dropped. She remembered the beginning of the traumatizing story they had read online. Strange ass shit happened in Gravity Falls, so she wouldn't be surprised if the story was a gypsy story or some shit. "Uhhh, Dipper, we should get going… I… uhh… have homework." She said. "Come on, Mabel, it's just a forest. See?" Dipper replied, spreading his arms. "Nothing to be afraid offff…." He trailed off, seeing his great uncle grab an axe off a tree. He, too, remembered how the fucked story they read began. "MABEL! DUCK!" He screamed. It was too late, though. Grunkle Stan had kicked Mabel in the back, and she tried to let out a scream, but was cut short but her Great Uncle, who stomped his foot as hard as he could into her legs, turning the scream into a small yelp. Dipper probably could have escaped then, but Grunkle Stan knew he loved his sister too much to abandon her to her rampaging Grunke. Sure enough the dumbass boy knelt down to the crying girl to pick her up. Mabel tried to mumble her gratitude to her brother, but he hushed her and told her everything was going to be ok, casting a horrified look at his uncle, who, while this was happening, just watched, enjoying the heartbreaking scene. Dipper started running, but his much larger Grunkle easily reached for the hood of his sweatshirt, and he tripped, Mabel falling down ontop of him, and knocking the wind out of him. While he recovered, Mabel lifted herself by her arms and saw her great uncle, with the axe above his head. Just as she was bending back down to move her brother, or drag him out of the way, or anything, the Axe was smashed down into her head, then lifted, as Dipper had finally came to his senses, only to let loose a bloodcurdling scream as an axe was thrown down into his tender skull. And again. And again. And again. Stan continued to laugh and smile as he smashed the heads of his twin niece and nephew repetitively with the axe. He picked up the bodies and walked back to the shack.
Entering through the back entrance, Stan quickly butchered the bodies and disposed of the clothes, heads, faces, etc, anything that could identify the two chunks of meat as Mabel or Dipper. Once he had cooked them, he called Wendy down from the gift shop, told Soos he could take a break with the lightbulb he was fixing, and called down to his basement dwelling brother, Ford, for a surprise Pork dinner. Everyone enjoyed a meal of the two Pines twins, thinking it was Pork. They all finished and told Stan the meal was great. Once everyone had gone back to doing their job, Stan then sat down at his computer desk. He went onto the website , and logged in. He then clicked on one of his two stories. Once the page had loaded, he began reading the reviews of his story, Grunkle Stan Kills his Friends and Family, which he wrote as a warning message to the twins. Once he was satisfied, he logged out of his account, and left to go finish his job. And yes, by this logic, Grunkle Stan wrote this story…
And that means…
I am Grunkle Stan. Killing the kids was fun.