Weiss was utterly aghast as she entered the dorm room. She found Ruby sitting on the bottom bunk, Weiss' bed, looking utterly enormous. Ruby had somehow fattened herself to ludicrous proportions, enough so that she almost looked round. Her gut looked even more spherical crammed into an arctic blue tracksuit, which was almost skin tight on her. Her sleeves were like sausage casings containing her ham hock arms, her pants were pulled tight by her incredibly wide hips and her enormous thighs, her whole outfit creaked almost as much as Weiss' bed. Even her fingers looked pudgy, wrapped around a little brush that Weiss took a long moment to notice.
As Ruby heard the door open, she turned to Weiss, revealing her round, double-chinned face, as well as the small patch of violet body paint on and around her nose.
"Oh, hey Weiss, sorry for not asking to use your mirror, but I couldn't fit through the bathroom door," Ruby said, awkwardly rubbing the back of her head.
"Ruby Rose, what on Remnant have you done to yourself?!" Weiss shrieked, recoiling somewhat.
"It's for the costume party tonight, silly," Ruby casually dismissed. "What, have you never seen Chartreuse and The Chocolate Factory?" Ruby could almost literally see the cogs turning in Weiss' head as she processed this information, her face slowly morphing from shock to confusion.
"Char… what?"
"Yeah, there's this girl in it that has some bubblegum, except it's all weird and turns her into a human blueberry. It's why I've got the paint," Ruby explained, pointing to the brush in her hand.
"O-oh… I see… I'm sorry for overreacting, I'd forgotten about the party tonight," Weiss responded sheepishly, before a realisation hit her. "Wait, then how are you so big?"
"Bought some dust online. Should only last a couple hours, I tested it last weekend when you three were out," Ruby mentioned.
"Right, right, I see…"
"Oh, Weiss, could you could help with the paint? I gotta do my face and hands, but it's easier if someone else does it. Then, maybe, I can help with yours," Ruby offered, making Weiss cringe as she realised something else.
"I… don't actually have a costume for tonight," Weiss admitted. Ruby pursed her lips in thought for a moment before she lit up like a lightbulb.
"Ooh, I've got an idea! I have a spare Violet costume, we can match!"A few hours later, the duo was at the party, both immensely fat, crammed into their tracksuits, their skin painted purple. Weiss felt like the costume didn't work as well on her as it did on Ruby, as Ruby had that massive, round belly, whereas Weiss had a massive rear and chest and a comparatively modest belly, even if it was still the second largest in the room by a long shot. However, it beat the embarrassment of no costume, and she saw the appeal of being so soft. Maybe she should order some of this dust for herself, she thought.
{AN: Used my old reliable wheel of prompts and got "RWBY Wonka", spun again to see if I got something that would be more interesting and got "Cosplay", then my brain went "Hey, what if you did both?" and then this happened.
Also, this is the closest I'm ever gonna get to writing actual blueberry stuff, it's super "not my thing".}