Fluttershy sighed as she looked at her two scientist friends. She had come to them with a problem - her breast hypertrophy and increasingly large bustline were putting a serious strain on her back. While the most common course of treatment was either a breast reduction surgery or having them two of them make a magic potion that stopped her breasts from growing (Fluttershy seriously did not count this out, given what she’d seen since that Fall Formal back in high school), Fluttershy was actually secretly proud of her abnormally large breasts. So Twilight Sparkle and Sunset Shimmer has come up with an amazing solution - a potion to make her back stronger. Now they were ready to test it.
 
“Are you sure you want to do this, Fluttershy?” Sunset asked.
 
“Yes, Sunset,” she answered, “I’m certain. Maybe if this had been back in high school I would have tried another solution, but the years with you girls have taught me to love my body the way it is.” She giggled. “Or will be, if I keep growing like this.” With that, the pale yellow girl began to undress, removing her shirt from her head-sized breasts.
 
“Uh, Fluttershy,” Twilight piped up, “what’s with the bikini?”
 
“Oh, uh,” Fluttershy stammered, “these were the only undergarments that would fit me after my most recent growth spurt. Any bras I have just hurt way too much.”
 
“No judgments here, remember,” Sunset said as she put her arm on the pink-haired girl’s shoulder. “And I think it looks damn sexy!” the flame-haired girl said as she walked over to where Twilight was adding the final ingredients to the solution.
 
Fluttershy blushed furiously at that. While they were all used to Sunset’s teasing by now, it could still shock the shy girl from time-to-time.
 
She then took the opportunity to look down at herself - or as much of herself as she could see past her giant boobs. Except for said sweater boulders, the rest of her was model-thin. Not for her the toned athletic build of Rainbow Dash, or Applejack’s frankly impressive muscles, or Rarity’s more traditional hourglass figure, or Pinkie’s perfectly-proportioned pudge. Even Twilight and Sunset, whose breast sizes were both close to “impressively large”, had a more generously padded rear than the top-heavy girl standing in the room with them.
 
‘Well, maybe one of the things this formula will do is give me something to counter-balance the weight on my front,’ Fluttershy thought to herself.
 
“Alright, everything’s ready, Fluttershy.” Twilight’s statement broke through the bikini-clad girl’s reverie. “Just take a sip of this and your weight problems should be over.”
 
The bespectacled scientist strode towards Fluttershy and handed her a glass containing what looked a lot like colorless cooking oil. Seeing her confusion, Sunset piped up. “Yeah, most people think that chemistry is about mixing a bunch of technicolor fluids together, but most organic chemicals, and even a lot of magical ones, tend to be a bit more dull.”
 
Fluttershy looked at the contents of the glass one more time, before taking a drink. She almost gagged. Not only did it look like oil, it tasted, and - more importanly - felt like oil going down her throat. She quickly handed the glass back to Twilight, grimacing. “Yeah, sorry. You can’t really add flavoring or thin down the solution as that would affect the outcome.”
 
“So how long do I have to -ooh!” Fluttershy’s question was interrupted by a sudden rush of heat to her body. “I-I see now why you said I’d need to strip off my clothes,” she said as she fanned herself.
 
“Is this level of temperature increase normal, Sunset?” Twilight asked.
 
The orange girl responded, “Not this much, we may have miscalculated the dosage increase of the musculature enhancing potion.” Sunset watched a bead of sweat roll down Fluttershy’s bicep.
 
Wait, bicep?
 
Both scientist and mage watched as Fluttershy’s musculature quickly grew to “athletic” then “bodybuilder” then beyond as the mix of chemistry and alchemy worked on her body. Far from just increasing the strength of her back, the formula went overtime on the rest of her body too, causing dozens of pounds of muscle to appear on the formerly thin animal lover. Sunset also noticed (not that she was specifically looking at Fluttershy’s chest, she swears!) that the formula also appeared to be causing some breast growth as well.
 
After about ten minutes of growth, everything seemed to stop. The blue-green bikini that served as Fluttershy’s undergarments now barely did so, the top stretched heroically over her torso and breasts, while the cups has lost the battle to cover the now enormous nipples, not to mention the now trashcan-lid-sized areola. Her breasts had probably grown to ten times their previous size, large and full but still squishy enough that the overworked top was able to indent the flesh and make it hard to judge her true size. The bottom had fared better, mostly because the growth of her abdomen hadn’t really kept up with the rest of her, though her new 8-pack abs could probably win bodybuilding shown all by themselves. Her legs had grown too, now mighty pillars that Applejack would be envious of, each thigh as wide as an oil drum, and her calves took an almost 90 degree turn from that into her ankles. Her butt, from what could be seen, had probably ballooned out to about twice the width of a standard door.
 
Where the overgrowth had truly happened was her torso. Massive traps reached a foot or more above her head, converging with giant shoulders that looked like pale yellow big rig tires. Her biceps were now truly gigantic, and were possibly even bigger than her breasts now, nearly doubling the width of her torso, while her comparatively smaller upper arms were still the size of her abdomen. From what Twilight and Sunset could see, her sides and back had also spread out, although they couldn’t tell by how much given the fact that her arms and breasts stood in their way.
 
Fluttershy tried desperately to cover up her nipples, failing utterly given both their size and the awkwardness of moving her newly massive arms. She was blushing furiously, though from the residual heat of the formula or sheer embarrassment neither of her friends could tell.
 
“You wanna sip?” Sunset said after a while of staring at the pale yellow mountain in front of them.
 
“Maybe we should call Rarity first?” Twilight responded. “So, you know, Fluttershy can get some clothes?”
 
“And maybe the other girls?”
 
“Yes, definitely! We need to see if this was a problem with the mixing of the formula or because of Fluttershy’s genetics or both!”
 
“And totally not because we want to our friends grow into sexy, muscular behemoths.”
 
For some reason that made Fluttershy blush even harder.
 
_____  
Commission I got from AutumnMelody AutumnMelody  
Too many words about a picture by me