The red sky of Weirdmageddon hung heavy over Gravity Falls, a grotesque tapestry stitched with nightmares. Buildings floated at impossible angles, twisted faces leered from every surface, and the air crackled with chaotic energy. Dipper Pines, his twin sister Mabel, and their Grunkle Stan stood on the precipice of the final battle against Bill Cipher, the triangular demon who had turned their world upside down.

Ford, Stan's brilliant but socially awkward twin brother, adjusted his goggles, his six fingers twitching nervously. "Right, Stanley, we need to focus. The plan hinges on you remembering the incantation. It's vital we perform it correctly to weaken Bill's hold on this dimension."

Stan, ever the pragmatist, scoffed. "Relax, Ford. I ain't forgot nothin'. It's right up here," he tapped his temple, "lodged between me and him." He gestured with a meaty hand towards Ford.

Ford, a man whose scientific mind thrived on precision, winced. "Stanley, for the last time, it's 'between him and me.' The object pronoun comes after the preposition."

Stan's face flushed crimson. "Oh, here we go again! Always gotta correct me, don't ya, Poindexter? I'm trying to save the world here, and you're worried about grammar rules?" The red sky seemed to mock him, its unnatural hues mirroring the rising anger on his face.

Dipper, ever the strategist, knew a full-blown argument between the Pines twins at this critical juncture would be disastrous. Bill Cipher was already powerful enough; they couldn't afford to give him any more advantages. He needed to diffuse the situation, and fast.

Thinking on his feet, Dipper blurted out, "Actually, Grunkle Ford, I think you're the one who's got it wrong."

Both Stan and Ford turned to him, surprised. Mabel, who had been busy trying to cheer up Waddles with a glitter bomb (which Waddles promptly sneezed all over Gideon Gleeful, adding another layer of weirdness to the already bizarre scene), also paused to listen.

Ford raised a skeptical eyebrow. "And what makes you say that, Dipper? I have dedicated my life to understanding the intricacies of language and dimensional physics. I assure you, my grammar is impeccable."

Dipper swallowed nervously. This was a risky move, but he was desperate. He knew Ford's penchant for intellectual challenges. "Well," he said, trying to sound confident, "the preposition 'between' requires a plural object. Therefore, it should be 'between him and I.'"

A stunned silence fell over the group. Even the floating eyeballs seemed to blink in disbelief. Stan's anger deflated like a popped balloon, replaced by a mixture of confusion and amusement.

Ford stared at Dipper, his numerous fingers drumming against his journal. A complex expression flickered across his face – a mixture of disbelief, annoyance, and a grudging respect.

"That's… a rather creative interpretation, Dipper," Ford finally said, his voice tight. "However, it's fundamentally incorrect. While 'between' does connect two objects, those objects are governed by objective case. It functions as a preposition introducing a prepositional phrase, and thus requires objective pronouns."

Dipper knew he was grasping at straws. He was no grammar expert, but he'd remembered a vague rule from school and hoped it would be enough to distract them. "But," he argued, pushing forward, "doesn't the proximity to the verb 'is' in the implied clause 'it is between him and I' make 'him and I' the subject complement? Shouldn't it be nominative?"

Ford's eye twitched. He opened his mouth to retort, then closed it, a vein throbbing in his forehead. "That's… an interesting way to approach it," he conceded, his voice laced with a hint of begrudging admiration. "But your reasoning is flawed. The implied clause is not a formal grammatical structure in this context. The 'between' still governs the pronoun usage."

Mabel, sensing an opportunity to lighten the mood, skipped forward and wrapped her arms around both Dipper and Ford. "Guys, guys! Who cares about grammar right now? We're in the middle of Weirdmageddon! Let's just focus on kicking Bill's butt!"

Stan, still slightly dazed, chuckled. "She's right. Besides," he clapped Dipper on the back, nearly sending him sprawling, "kid's got guts, I'll give him that. Tryin' to outsmart Ford with grammar? That takes some serious chutzpah."

Ford sighed, running a hand through his already disheveled hair. "Fine, fine. We'll table the grammatical debate for after we've saved the universe. But mark my words, Dipper, we will revisit this."

He turned back to Stan, his expression serious. "Stanley, focus. The incantation. Are you ready?"

Stan straightened up, his gruff exterior hardening into a mask of determination. "Born ready, Ford. Let's send that triangle-headed freak back to whatever dimension he crawled out of."

With renewed resolve, the Pines family prepared to face Bill Cipher. Dipper, though still slightly apprehensive about the impending grammatical showdown with Ford, felt a surge of hope. He had managed to avert a fight, at least for now.

The battle that followed was a chaotic whirlwind of magic, science, and sheer Pines family stubbornness. Ford, using his knowledge of dimensional rifts, created a temporary shield around them. Mabel, armed with her boundless optimism and a grappling hook, managed to disorient some of Bill's henchmen. Stan, fueled by righteous anger and a lifetime of pent-up frustration, charged forward, ready to punch anything that moved.

Dipper, meanwhile, used his knowledge of Bill's weaknesses, gleaned from Journal 3, to guide their attacks. He knew the incantation was their best chance, but the chaos made it difficult for Stan to concentrate.

Bill, seeing his carefully constructed nightmare crumbling around him, roared with fury. "You pathetic humans! You think you can stop me? I am the master of this dimension!"

He unleashed a wave of chaotic energy, shattering Ford's shield. Debris rained down around them. Mabel was knocked off her feet, and Stan stumbled, momentarily forgetting the incantation.

"The incantation, Stan! Focus!" Ford yelled, desperately trying to repair the shield.

Stan struggled to remember, his brow furrowed in concentration. "I… I got nothin', Ford! It's gone!"

Panic threatened to engulf Dipper, but he couldn't afford to lose hope. He looked at Stan, his eyes pleading. "Grunkle Stan, you can do this! Think about everything you've fought for! Think about your family! Think about protecting Gravity Falls!"

Something in Dipper's words struck a chord. Stan's eyes cleared, and his jaw tightened. He took a deep breath, his voice resonating with newfound conviction.

"Alright, triangle-face," he bellowed, "time for you to learn a lesson about messing with the Pines family!"

And then, with a voice that echoed through the chaotic landscape, Stan began to chant the incantation. The words, ancient and powerful, flowed from his lips, filling the air with a tangible energy.

Ford, seeing his brother's resolve, joined in, his voice harmonizing with Stan's. The words became a beacon of hope in the darkness, a testament to the power of family and determination.

As the incantation reached its crescendo, a blinding light erupted from the center of Gravity Falls. Bill Cipher screamed in agony as his power began to wane. The red sky started to fade, and the twisted landscape began to revert to its former state.

The fight wasn't over yet, but the tide had turned. Bill Cipher was weakened, vulnerable. And the Pines family, united in their determination, were ready to deliver the final blow.

Even after Bill was erased from existence, and Gravity Falls started to heal, Dipper knew he couldn't escape the inevitable. As they stood amidst the recovering town, watching the vibrant colors return to the sky, Ford turned to him, a glint in his eye.

"Now then, Dipper," Ford began, his voice deceptively calm. "About that grammatical 'correction' of yours…"

Dipper braced himself. He knew this was coming. He had distracted Stan and averted disaster, but now he had to face the consequences of his audacious, albeit strategically-motivated, grammatical faux pas.

He gulped. "Yes, Grunkle Ford?"

Ford smiled, a rare but genuine smile. "I have to admit, Dipper, your attempt to use grammar as a weapon was… surprisingly effective. And while your understanding of the objective and nominative cases requires significant refinement, your quick thinking was commendable. But," Ford's smile faded, replaced by a stern expression, "that doesn't excuse the fact that you were completely, utterly, and demonstrably wrong."

He then proceeded to deliver a comprehensive, hour-long lecture on the intricacies of prepositional phrases, pronoun cases, and the subtle nuances of the English language. Dipper listened attentively, occasionally interjecting with a question or a counter-argument, but ultimately conceding to Ford's superior knowledge.

As the sun set over a newly restored Gravity Falls, Dipper finally understood. He had learned a valuable lesson, not just about grammar, but about the power of family, the importance of quick thinking, and the unwavering dedication of Grunkle Ford to the pursuit of knowledge, even in the face of interdimensional chaos. And even though he still felt a twinge of embarrassment, he knew that he wouldn't trade that experience for anything. After all, it was all part of the weird and wonderful adventure that was life in Gravity Falls.