Octavia made her way home from the market square with that day's groceries. As the cellist neared her home, which was just that she and her roommate lived on the edge of town. It had been four months since Vinyl's butt had first expanded. Ever since then her rump would occasionally start to swell again for thirty seconds before it would stop. At this point, Vinyl's backside was easily twice the size of the house if not bigger. Thanks to that, Vinyl wasn't able to walk or even stand up anymore. Octavia did feel sorry for her friend though. Even still, Octavia couldn't help but smile a little at the situation. Octavia absentmindedly fingered her necklace as she walked. The cellist got it a few weeks after Vinyl's ass had first expanded. It was rather simple in it's design. It had a small ruby in the middle of a treble clef which hung just above her cleavage. Something about it helped her stay calm through the whole ordeal. Octavia did noticed that some of her clothes didn't fit properly soon after. She just chalked it up to them shrinking slightly in the wash. As Octavia entered the house, she could hear her roommate muttering something in what was once the living room.
"Is everything okay Vinyl"? asked Octavia.
"No, my fat ass grew again. It's the fifth time this month." replied the former DJ.
Octavia sighed and went to the kitchen to put away the food. Once done, Octavia rejoined Vinyl in the former living room to see if she could lift her friend's spirits.
"Cheer up, Vinyl. Hopefully, your posterior will stop growing eventually." said the cellist putting a hand on Vinyl's shoulder.
"Kind of hard to do when one's ass gets bigger every other day." responded Vinyl lightly tapping her rump.
"True enough. Well, in case. I need to get ready for a dress rehearsal soon. Fortunately, it should take only an hour. I'll try to return home quickly." said Octavia heading towards the bathroom.
"Alright. Do try to hurry back. I think it's going to rain tonight." answered Vinyl turning the television on.
As Octavia took off her clothes, the cellist toyed with the idea of taking her necklace into the shower. Octavia ultimately decided to risk it and kept the necklace on. Unbeknownst to the mare, the necklace started to give off a soft glow as she stepped into the shower. Octavia let out a sigh of relief as the warm water washed off the morning grime. As Octavia cleaned herself, the cellist noticed that she started getting a tingling sensation in her breasts. Octavia looked down at her chest to see what was the matter. Only see in horror that her bosom was growing. Turning off proved to be useless task as Octavia's tits continued to expand. By the time Octavia found a towel, her breasts were as big as her head. Octavia barely managed to get through the bathroom door due her enlarged size. As she made her way back to the living room, Octavia's bust only got bigger. They were nearly twice as big by the time Octavia reached her destination.
"Sweet Celestia. What in Equestria happened to you, Octavia?" asked Vinyl when she spotted now buster roommate.
"Not sure. I was just taking a shower when." answered the cellist before letting a moan of pleasure as breasts suddenly surged in their growth.
It was when leaned forwards because of her new weight, that Vinyl noticed her friend's necklace glowing. She pointed it to Octavia, who promptly removed the thing. The task proved to be just as effective as turning off the shower. Octavia could only watch as her breasts continued even bigger. After a couple of minutes, Octavia's boobs finally stopped expanding. Her chest were nearly twice her size and were barely touching Vinyl backside.
"Well. My day is ruined." said the cellist somewhat upset at the situation.
"I feel your pain Octavia." responded Vinyl lightly patting her ass.
Once Octavia had calmed down, the mares tried think of what to do next. Unfortunately, either Octavia or Vinyl could come up with a proper solution.
"The best thing we can do right, is to wait and hope somepony notices I never showed up and comes looking." Said Octavia.
"I guess. In the meantime though. Want to watch some T.V.?" replied Vinyl
"We don't have anything better to do." Said Octavia as she did her best to reposition herself
Two months came and went since the strange incident, Octavia's breasts greatly increased her bra size. Like she had thought, when Octavia failed to appear for the dress rehearsal, a member from her orchestra band had came calling to see what happened. They got their answer when the entered the living room. Octavia had explained what cause the problem and asked for Princess Twilight Sparkle help. Fortunately, Twilight knew exactly what kind of necklace that Octavia had. The downside was cutting off what connection would have to have the cellist stay home for a month at least. Since then, Octavia's band mates and close friends would drop by daily to check on the two mares and to help with food.
"Thanks again for coming by today, Lyra. Tell Bon Bon, we say hi.""said Octavia waving goodbye to the mint green unicorn
"Is it just me? Or was Lyra a bit handsy today?" asked Vinyl.
"She's always been like that. Although, you do have a point. Lyra was kind of excessive today." replied Octavia.
"That's putting it mildly. I'm just glad my ass finally stopped growing." said the DJ.
In the two months since the necklace bound itself to Octavia, Vinyl's rear end had one last big growth spurt. It was now the size of the castle of friendship. This made Octavia thankful again, that she and lived on the edge of town. For the rest of the afternoon, the two mares discussed what they should do next in life. It wasn't until early evening, that the musicians got an unexpected guest in the form of a very well-endowed mare. She wasn't as big as Octavia, but her breasts were half the of her entire torso. Apparently, her name was Milky Way and she was Octavia's friend back in the day before Octavia went to college.
"What brings all the to Ponyville, Milky?" asked Octavia
"Well, I'd heard that a well known cellist suddenly got a much bigger bra size. I just had to see it for myself. But, I never thought you'd get this big, Octavia." replied the pale yellow the earth mare.
Octavia explained to her old friend what happened to her and her roommate. Milky Way shocked to hear that a batch of cookies and necklace were able to cause all of this. As the sun fully set over the horizon, Octavia offered Milky Way one the free bedroom. Milky tried to decline but Octavia wasn't taking a no for an answer. Milky sighed and accept the offer. Milky Way bid her hosts a goodnight as she headed off to bed.