Original story credit goes to yyy24.
As they wandered through the streets of a city that was similar to, but not quite like, Metropolis, Harley couldn't help but gawk at the bizarro-world around her. The most obvious feature was that everyone was fat. As in, everyone was fat. Fat enough that this universe's fat version of herself was a little on the light side. Fat enough that she saw elementary school-aged kids twice her weight. Even the pets were fat; she saw someone walking a dog that was probably heavier than the kid. Everything about the city seemed to revolve around eating. Every large flat surface was plastered with posters promoting some sort of artery-wrecking fast food product, people had (very stretched-out) tattoos of their favorite chip brands like people back home would have gang signs, and every corner had some sort of restaurant, stall, or cart hawking something that inevitably had the words "triple-" and "fried" somewhere in its name. She looked up, but above her were endless spires of illuminated restaurant billboards and neon soda signs. And of course, everyone was carrying a cup, bag or wrapper of sorts, and the only time something came out of their mouths rather than going in was when they belched.
Then there were the smells. Harley wondered why her alternate self hadn't started going by the name Pennywise, considering how the entire city smelled like a sewer. Every surface people touched seemed grimy, there were puddles and stains of very questionable repute all along the sidewalk, and the air itself seemed to be filled with a foul-smelling haze. Harley wondered what it would be like to light a match in there.
She couldn't shake the feeling she was being watched, though, and she wasn't exactly wrong. Whenever she caught someone's eye, they would either stare at her like she'd grown a second head, or give her a dirty glare worthy of blood feuds and people who cut you off in traffic.
"So, uh, me, why are we going so far and passing all these other places?" Harley asked, shouting over the din of traffic and flatulence.
Her larger companion slowed down to a normal-paced waddle and let her catch up. "Oh, these places? I've eaten at every one of 'em at least half a dozen times. They're all good, but they ain't nothing special. If all these other places are blowin' your mind, wait until you see this place!" And with that, they stopped in front of a place that looked like a rather upscale establishment; black walls, silver building accents, nice mahogany doors, lines of people waiting to get in, and two bouncers with big paunches who could probably throw bigger punches.
Large Harley grabbed her and put a heavy arm over her shoulder, whispering, "Just follow my lead and keep quiet." Harley had no trouble with staying quiet, though her gag reflex was a different matter; Large Harley's armpit was right by her head, and all the leather and spandex in the world couldn't keep the odor from staying in.
Harley didn't focus on what her corpulent counterpart was doing compared to holding her breath, but somehow they got through the doors and were quickly escorted to a booth. When Harley was free of her companion's fleshy prison, she took a massive gulp of air. Big mistake. The stench of the outside was even more overpowering here, and she could hardly breathe without trying to not throw up. Big Harley, meanwhile was having the time of her life.
"What, you're gagging at this?! You can't be serious! If this is bad for you, then I'd hate to see you in my bathroom the day after One Buck Burrito night!" she snorted before launching into another fit of flatulent giggles. When it died down, she resumed talking, "I already ordered us the three-course special. Believe me, you'll love it!"
After that, the conversation died down significantly, with the silence occasionally being broken by gas escaping from one of Large Harley's ends. Thin Harley was bored out of her skull; there were no napkins to tear, silverware to throw at people, plates to spin (and promptly break), or menus to read the fine print of. The only other thing on the table was a bowl full of cake-like sugary bread rolls stewing in melted butter. Harley had stopped after a couple bites, but her fat friend had already eaten half the basket and began pouring butter into her overflowing mouth, rendering her spandex-clad front a little too transparent for Harley's tastes.
"So..." Harley said, attempting to broach the awkward silence, "how did everything get to become so, ya'know..."
"Big?" Large Harley aptly replied. "Well, I'd say it all started, I dunno, twenty or thirty years ago. I mean, when I was younger, everyone was still pretty thin. Then, I guess bein' fat just started becoming popular, then just normal. When I went into high school, I was 150 pounds. When I graduated, I was just over 200. Almost 300 when I met Mister J, and now, I'd say I'm easily past 500. I was around 400 or so for most of my life, but then..."
Harley, now engrossed in this weird world, eagerly asked "...and then what? C'mon, tell me!"
Large Harley sighed (which was cut off prematurely by a burp), "It happened. It all started when-"
Before she could say another word, a massive waitress on a motor scooter with a body like Jabba's and hair like Chewbacca's rolled up and placed two massive soup-tureens that rested on her belly up on the table. "Order up! Special, first course, two servings!" Without another word, she sped off back to the kitchens. Harley wasn't sure whether the puttering noise was from the cart or from her ass.
Harley cautiously lifted the lid off and wanted to gag. Inside was a churning pool of what looked like half-congealed fryer oil, its surface obscured with lumps of fried dough, mystery meat, and a few unidentified white globs. Once again, Large Harley saw her smaller self's reaction and had another laugh at her reaction. "What, you've never seen melted lard mixed with mayo before? That's a piece of deep-fried chocolate cake, that's some mozzarella, and the meat? I wanna say it's beef. I dunno, they change it every week."
Her fears (very slightly) assuaged, Harley nervously leaned over, filled her ladle-sized spoon, and apprehensively took a sip. Her tongue felt like it had been taken a wrong turn down an alley, got whacked by a stick of butter, and was robbed of all its tastebuds. The flavors were so powerful and overwhelming it was as if they canceled each other out, leaving only a vaguely buttery taste. A glance across the table showed her large counterpart earning her name, desperately slurping down soup and picking out floating chunks of food with her bare hands. Harley didn't want to be rude; her friend (for lack of a better word) had arranged this all, and she didn't want to make her bad or seem even more out of place than she was already. Besides, she thought, how much damage can another sip do?
...
Harley moaned in a combination of pain and ecstasy, her hands rubbing her swollen midsection. She hadn't packed away the soup like her larger self, but a good third of it was empty and all the chunks of food were picked out. She didn't necessarily want to feel like she was pregnant with triplets, but a combination of interdimensional peer pressure and a bit of actual hunger forced her to each as much as she physically could without being sick.
Harley glanced down at her swollen stomach. It only peaked out several inches, but as far as she concerned, she might as well be carrying a boulder in her belly. "Oh god," she mumbled, her eyelids fluttering a bit. "I'd say I definitely overdid it. Food wins." The ladle slipped out of her hands with a clatter and Harley closed her eyes, listening for a moment to the sounds of her larger self pouring the remaining contents of Harley's soup-tureen into her own.