"A long time ago, a young mare lived in a house by a river. One day, while she was taking a walk down that river, she saw a basket floating down in the current, and curious she used a nearby fallen branch to grab it and take it out of the water.
Looking inside, she found a spool of thread and a needle. The thread seemed to shift colour in the light, and she was unsure of what material it was made from. She decided to take it to the tailor who lived in the town, to ask if it was his, but he said that he'd never seen anything like it.
After studying it for a while, the tailor asked her if he could keep it and try to use it, and seeing how she had no experience when it came to sewing she accepted. The tailor thanked her, and she went back to her home.
The next day, she was awoken by the sound of someone knocking at her door. She went to see who it was, and found the tailor. He was shaking with excitement, and once she invited him to sit inside he explained that the thread she'd found was magical. It perfectly merged any two pieces of fabric into one, it never ran out, and it somehow seemed to enhance the qualities of every dress it was used on.
The tailor wanted to repay the mare for her gift, and he asked her what she wanted, and after some thought she decided to ask him to take her as his apprentice, something he gladly accepted.
Many years passed, the tailor becoming the most well renowned in the whole kingdom thanks to the magic thread and the mare learning to be even better than he was at the job by coming in contact with all the most famous stylists in the land. One day, in their boutique in the capital city, the old tailor called his apprentice to tell her something.
He explained to her that he was old, and that she'd become better than he was at the job. Therefore, he'd decided to retire and leave the business in her hooves, and before going away to live in a house he'd bought by a lake he gave her the magic thread.
The mare was ecstatic at the prospect of finally being in charge, and even more at the idea of finally getting to decide what to do with the thread for herself. She'd always wanted to try something, although she'd never had the courage to ask her teacher about it, and now she could finally do it.
Immediately, she locked herself in her laboratory and began to work. She would make a dress entirely out of the magic thread, and it would be the most beautiful dress ever made. She furiously, restlessly worked on it, not making a design before but instead letting her inspiration overtake her as she went, and after a full day of work the dress was finally complete.
Overexcited, the mare wore the dress and dashed out in the streets to show it to the world, but everypony who looked at her either began to laugh, turned their head away or simply appeared to be disgusted. The mare was confused, but as she saw her reflection in a puddle of water on the ground she understood. The dress was horrible. It was the worst thing ever designed and worn by a pony, the most hideous thing ever to appear in the world.
Screaming and crying, the mare ran back to her room and tried to take the dress off, but no matter how hard she pulled it seemed to be stuck to her, as if it had been sown to her skin, and nothing she tried was able to remove it, neither cutting it nor trying to burn it away. Unable to stand the sight of her creation she broke and threw out the mirror from her room, although the image she'd seen forever burned itself in her mind.
Devastated and terrified, the mare locked herself in her room and began to cry, and she stayed there for a whole week. After much crying and sadness, though, she devised a plan, one that would fix her problem. She was, after all, the most well renowned seamstress in the kingdom, and as long as she still had the magic thread she would remain as such, so she began to put her plan into action.
It was a slow one, one that would require years to be fully realized, but she persevered. Closed inside her room to prevent others from seeing her, she began with small alterations first. Shorten a sleeve here, use a different pattern there. Using the influence she had over the kingdom's sense of style and her reputation she slowly, subtly modified and directed the fashion sense of the population, until it would match with the dress she'd crafted.
The day finally came. All over the kingdom, nobles were wearing dresses that were but modified and inferior versions of the one she was trapped in. It would be her moment of triumph, to finally walk in the streets with what everypony would consider the perfect dress. And so the mare, now old and tired, finally got out of her room.
But as she began to walk down the streets, the looks she got were the same she'd gotten all those years ago. She was confused and couldn't understand what was happening, but once she reached the fountain in the centre of town and she saw her reflection she finally understood. All the things she'd made unfashionable by altering the trends, all the things that were now seen as undesirable in a dress, the one she wore had changed to reflect those, and was once again the worst dress possible.
The mare ran back to her room in tears, and never got out again. And to this day the dress is still with her, still being the most unstylish piece of clothing imaginable no matter the current tastes of the world."
"Your sister's got a real weird idea of what's scary," Apple Bloom silently muttered to Sweetie Belle.
Rarity pouted, slightly annoyed.
"She's got a point, Rarity," Rainbow said from up on the tree, "you focused on the wrong elements. Who wants to go next? Fluttershy?"
The yellow pegasus looked up, slightly startled. "Well, if no one else wants to go before me..."