It had been a few days since Frisk had fallen down into the underground. She had made quite a bit of progress, until she hit a roadblock. Getting past all of the puzzles and tricks that had been left for her in the Ruins had not deterred her, but it seemed her greatest foe was the one person, or monster in this case, trying to help them.
It was none other than Toriel, her friendly Goat Friend who seemed to take on a sort of motherly role for her. As much as Frisk wanted to leave, she couldn't just leave this friendly goat woman to be all alone. It would break her heart.
So Frisk just stayed behind and became a part of Toriels life for the passing days, not bothering with escaping just yet. Besides, the pies she made were delicious. As much as she hated to admit it, she had a bit of a sweet tooth, and couldn't just let things like pies go to waste. Even though just one slice always intimidated her, Frisk was determined to, someday, have the courage to take on the entire pie.
So that's what Frisk did, just hung out with her Goat Mother, having her read her bedtime stories, playing outside, learning lessons and snail facts. Everything seemed perfect, nothing could go wrong.
But, of course, that's also everything wrong. Frisk knew she couldn't just stay trapped underground her entire life, she needed to go and experience the rest of the world, escape to see the friends and family she had on the surface world. With these thoughts constantly going back and forth, whether it was better to stay or leave, these questions simply would not leave her head until, finally, she came to a decision.
While Toriel was reading a book by the fire, and Frisk was drawing a picture of what they remembered her home looking like on the surface, with stick figures representing her mother, father, and herself, she looked up to Toriel, and decided to ask the question.
"Hey, Mom?" Frisk said, trying to get Toriel's attention. She had gotten used to calling Toriel 'Mom', as she played such a similar role, as well as seemed to enjoy being called that.
Toriel looked down from her book and asked, "Oh? What is it, my child?"
Frisk gulped, a bit afraid to ask, "Well... I've been thinking, after the past couple days... I don't think I can stay here anymore."
Toriel didn't make any noises. She just looked back at her book in surprise, "Wh... What do you mean, child?"
"I mean, I think I should start going. I need to get back to my family." Frisk mentioned.
"B... But... Aren't I family? You call me Mom..." Toriel asked, a bit downtrodden.
"I mean my own family. I'm sorry... Toriel..." Frisk said, feeling a bit guilty as well. But this had to happen, it was the truth. She couldn't keep lying to herself or Toriel like this anymore. This is what had to happen.
Toriel closed the book she was reading, and stood up. "I'm... Going to go somewhere. Please wait here." She said, before leaving the room and heading towards the basement.
Frisk, a bit worried, decided to disobey Toriel. Instead, she went after her, hoping to get some answers and possibly escape.
Upon reaching the basement, she noticed it had a much different design than the rest of the ruins. Pure purple walls, a broken cobblestone pathway. Toriel stood in front of her, and upon getting closer, she began to speak.
"...Go back upstairs, child." She stated simply, before rushing up ahead.
Frisk followed.
"...There is nothing for you to see. Go upstairs. Now." She said again, more sternly. She rushed up ahead once more.
Frisk followed briskly.
"...Up ahead is the door that separates the Ruins from the rest of the Underground." She began to explain, realizing her attempts to return Frisk to her room were in vain. But still, she moved on ahead.
And still, Frisk followed.
"I am going to destroy it. To make sure nobody leaves here again." Toriel stated, upon reaching a turn. She made the turn, and headed upwards towards the door.
Frisk continued following Toriel.
"This is your final warning. Turn back now, or face the consequences." Toriel demanded. She seemed serious.
Frisk, after taking a deep breath, followed Toriel until they reached the door. At this point, Toriel froze, and turned around, facing the child she had taken care of for the past few days. The tension was rising high.
"So. It seems you're adamant on leaving. So be it. If you want to escape... Well... I won't let you. I'll make sure you stay here, and never leave." Toriel stated, beginning to channel a magical spell. In her hands, a bright light began to emanate.
Frisk prepared herself to dodge an attack, until she smelled something... Familiar. A delicious scent that radiated from the hands of Toriel. Upon closer inspection, it seemed that Toriel had created a Butterscotch-Cinnamon Pie! It was absolutely massive, even larger than the pies that she normally baked.
"I'm normally an advocate for healthy eating, but... I'm afraid this is for your own good, child. Eat up!" Toriel said, as she took a slice of the large pie, and aimed it for Frisk's mouth.
Frisk, wondering what their game was, decided to play along for now. She grabbed the slice of Pie, and began to eat it up. The slice alone was the size of a basketball, and was loaded with butterscotch and cinnamon. Regardless, Frisk seemed to be eating it quite easily. When she finished that slice, she licked her fingers, patting her stomach.
"Have another, my child." Toriel said, handing Frisk another slice, to which Frisk graciously accepted. It was mostly her sweet tooth which is why she was unable to deny sweets, so this made her figuring out Toriel's true motives very difficult.
Frisk ate the slice, and upon finishing that one, she was offered another, and another, and another, the cycle repeating until the entire pie was devoured piece by piece. In the process, Frisk's belly was bloating up larger. Their stomach was poking out of their shirt and spilling over their legs and riding up her shirt, making it tighter as she ate more of the pie. But of course, Frisk was unable to keep herself from eating it, the pies were just too good! Her shorts were becoming tighter as well, showing off her growing thighs and ass more, making her growing, obese body more visible to anyone, if they could see it.
Once Frisk finished the entire pie, she was sat on her gigantic ass, which had begun tearing through her shirt and pants. Multiple rolls of fat squeezing out of her tight outfit, as well as giant breasts which had only come into existence due to her weight. She had a huge belly that reached out to her knees and was nearly the size of a yoga ball.
But Toriel wasn't done yet, while Frisk was busy eating that one pie, she had summoned in multiple others on top of that. "Don't worry, my child. There's plenty more where that came from..." She said, handing Frisk two more pies for her to wolf down.
Frisk, who wanted desperately to leave, was conflicted. Piles of delicious pies were right in front of her, and while she had already put on a ton of weight already, she couldn't just let them all go to waste.
But Toriel didn't give Frisk any time to think, simply stating, "Come on, eat it while it's hot!" Before shoving a slice into her mouth. This removed any chances of Frisk considering escape, now the only thing on her mind was eating these scrumptious pies.
So Frisk kept eating, each slice sliding down her mouth like smooth butter, filling her up like a lard-filled balloon. Toriel groped Frisk's belly, rubbing it and patting it as it grew into half her size. The clothes on Frisk soon became too small for her enormous body, and ripped off, leaving her in just her panties. But this didn't deter Frisk, as long as Toriel kept giving her more Pies, Frisk would keep eating.
Slowly, but surely, Frisk was filling up the room with her blubber, her multiple fat rolls overwhelming the area, but unfortunately Toriel was on the door side. She was being pressed up against the wall from Frisk's enormous belly, her asscheeks pressing up against the passageway towards the door to the underground, and her face is pressed up against the ceiling.
Frisk kept eating the slice of pie that she still had until the entire room began to shake and crumble around her. As her flab began to shake the very foundation of the ground, it wasn't long before the whole room collapsed and Frisk was left in what seemed like an empty void. It seemed that this room was much larger than Toriel had led on, and Frisk had a lot more space to cover.
At this point, Toriel had realized she had gone a bit too far with this. But at this point, she hardly cared. Frisk was so massive, jiggly and soft that all she cared about was making Frisk into the biggest ball of fat that the underground has ever seen.
Toriel got up off the ground and began to scale Frisk's massive belly, which rivaled that of her Home. Toriel used Frisk's various fat folds to scale her massive body like a rock climbing wall, fold by fold she would climb upwards. Climbing ever upwards towards the young child's blubbery face.
After a few minutes of climbing, she finally reached Frisk's face, who was happily asleep, seeming content with their massive weight. It seemed that both of them had found enjoyment out of this endeavor, and while at first Toriel was doing it to keep Frisk safe, now she only wanted to see Frisk get even bigger.
So, while Frisk slept, she began channeling a stream of Butterscotch-Cinnamon Pie-filling into her obese daughter's mouth, smoothly and softly, as to not wake her. As she did, she felt the body of her new, fat bed growing larger and wider. Soon the hallway in front and behind her was being crushed, and she was filling up the strange empty space that was below their Home.
Frisk chugged it all down, all in the comfort of her sleep, feeling herself beginning to outgrow the basement and burst through the floor of her old Home, destroying it into thousands of pieces. She also felt her stomach press up against the wall that separated the rest of the underground and the Ruins. The wall was easily destroyed, and Frisk still kept on growing, her blubbery belly now reaching the cold forests of Snowdin.
Toriel didn't even care how much damage she causes with this growing, obese child. All she wanted was to make her happy, and Frisk couldn't be happier.
More weight began to pile on, Frisk now covering half of Snowdin beneath her blubbery gut. In between her many folds were monsters, trees, rocks, rock monsters, tree monsters, and all other sort of things. Everyone in the town of Snowdin could see the immense, swiftly growing yellow blob in the distance, watching as it consumed everything in its path and spared absolutely nothing.
Everyone quickly evacuated as the Yellow Wall of endless blubber and lard crushed building after building, showing no mercy.
Toriel had begun to increase the flow of the Pie Filling, causing Frisk to grow even bigger. Perhaps if she grew large enough, she would outgrow the entire underground and free everyone! But did that matter to Toriel anymore? Did anything other than fattening up this child she met only a few days ago matter to Toriel anymore? What about Frisk? Was she happy like this? It certainly seemed that way, but what of the future? Would she be happy crushing everyone and everything in this world, constantly being filled up with this pie?
But it seemed that none of those questions were running through their minds. Toriel just continued filling Frisk up as she covered more and more of the Underground with her endless waves of yellow, blubbery fat, and both of them wanted nothing more.
It lasted all the way until Frisk began filling every corner of the underground, slowly rising up like dough in an oven, everything beneath her flattened beneath her endlessly growing and blubbery butt and belly. Endlessly waves and mountains of fat that jiggled about like jello, as she continued to chug more and more, Toriel feeding her and soon reaching the top.
Higher and higher, more weight continued to pile on top of itself, Frisk's face becoming absorbed by her impossibly high number of chins and cheek fat, her entire nude body pressing up against the walls of this hollow mountains until finally, she was beginning to reach the top. Her entire body filled the entirety of Mount Ebott, and the mountain itself was beginning to rumble and crack underneath the immense pressure.
Soon, thousands of rock shards went blasting off into multiple directions, and Frisk's fat flopped onto the ground, crushing everything around it. But Toriel wasn't done, she was going to make Frisk outgrow the entire world as well!
Toriel looked out, and saw the sun, and the ocean, and got one last look before it would all become covered in Frisk's immense flab. Toriel loved it so much, she snuggled a small fraction of Frisk's blubbery weight, nuzzling it and continuing the ceaseless stream of Pie.
Frisk, on the other hand, could see nothing but her own yellow, blubbery, obese body, but didn't care. All of this pie was enough to satisfy her. She felt her gigantic, twin buttcheeks crushing mountains, cities, skyscrapers, and her belly soon crashing into the ocean. She wondered if she was visible from space, which at this point she most likely was. A big, child-like blob growing rampant somewhere in America. Covering the entire world with their own gigantic blubber, thanks to a magical goat lady feeding her an endless supply of Pies.
This was certainly a good way for the world to go. After this, they had an entire universe to fill, as well, and so on, and so on...