My friend Jazzwolf347 and I worked together on this piece. I did the line art and she colored it in. Check her out, she's super coolio.
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Long ago, when Anansi was but a cub, he grew curious and chose to test his abilities. Under the cover of night, he snuck into Ponyville and began weaving a giant web over the town. For hours, he played around with ponies memories, switching them around and collecting the more interesting ones. Every memory a tiny bell that connected to an endless sea of bells by little strings. Ring one and the string would reverberate to another. One thought leading to another.
His main test subjects were the former elements of harmony. He'd read their journal and was curious to see how they'd fare if he messed with their memories. Would they change? Just how much had their experiences effected who they were now?
He had to know.
* For Rarity, he chose to take from her her lessons of humility and maturity, making her more like her season 1 self. She was dramatic as usual but less mature and pleasant to be around. Upon recalling her marriage to the great Lord Fancy Pants, she chose to spend the day showing off her hubby and their wealth. Fancy was very disturbed by this and some words were exchanged over the matter.
Neither ever talks about it since it was… a bad day for everyone.
* For Fluttershy, Anansi saw how many baby steps the mare had taken in her journey to being more assertive. He admired every step, no matter how minute, so he took them all. This left Fluttershy a nervous wreak, scared of everyone and everything, including her own husbands and children. The entire day was spent with her hiding somewhere while her family went looking for her.
* Rainbow Dash was one he had only a little interest in. She was loud and brash but surprisingly friendly outside of competition. Yet she wasn't always like that. She'd learned to curb her enthusiasm and accept other ponies weaknesses. So he took those lessons from her, making her arrogant and confrontational, pushing her own son into athletics despite her previous acceptance of his disinterest.
It'd take weeks before Tranquil would stop cowering in front of his mother, afraid she'll demand he 'try harder' again.
* Pinkie was the least noticeable to those outside her family. She was still her bubbly self even after Anansi manipulated her memory. Since he wanted to test how ponies in their lives affected them, he chose to remove the memory of her falling out with her father. He wanted to see how much being nearly disowned affected her. Surprisingly, not much though her son was wary of her that day. When asked, he'd just say that his mothers smile just wasn't right. She smiled but it felt fake.
* On the same branch, Anasi continued to take ponies from his test subjects memory, wanted to see the aftermath. Applejack was next and he chose to remove all the memories of her husband after they'd gotten together. So Applejack ended up waking up to the stallion who conned her various times, in her home making breakfast. As expected, she exploded at him, demanding to know how he'd gotten into her home. When Sweet sleepily asked why she was yelling, contradictory memories flooded into her, leaving her with a major headache. She chose to work through it, ignoring her husband and convinced this was some kind of scheme.
Cause why in Equestria would she ever marry that two bit swindler.
* Twilight suffered the most, entirely because Anansi in his young mind, wanted to push further. Too far. He quickly learned that not only experiences but those around you affect how one turns out. So far, he'd just cut a few strings and lefts holes in the towns ponies memory, allowing them to fill in the blanks themselves. But what if he didn't let the gap fill? How would it affect that pony? But he couldn't let it be something little like someone around them everyday. No, it wouldn't work if he did that. No, he had to dig deep and find something meaningful, a foundation of ones self.
So, he took Twilight's memories of Princess Celestia, a hole that she couldn't fill.
Due to a slight mishap, mainly because Anansi was too excited to be more careful, Twilight was the only one in Ponyville aware that her memories had been tampered with. She was left hollow and desperate, knowing she had lost something important but unable to recall who they were. She had loved this pony, had rested her very identity and life on their shoulders and now they were missing. Not only from the world but from her head.
Twilight had spent a lot of that day walking about aimlessly, searching for something she couldn't recall and growing more and more anxious as the hollow feeling grew bigger.