And Fluttershy isn't the only one. Strange transformations overtook several ponies, affecting them in different ways depending on their species.
A pair of unicorns, once identical twins, one half afflicted by the same malady. While the pegasus' bird wings warped and shifted, the unicorn's swirled antlers regrew into a fanglike shape.
Meanwhile, a young horse found herself with sharpened canines, shaggy fur - and just like the others - a hearty appetite for apple juice.
So what do these three have in common to undergo such drastic changes? Was it being in the wrong place at the wrong time? Or perhaps getting a little too close to nature during cider season.
The Flimflam brothers tried ripping up entire trees to press into substandard cider, earning the ire of wildlife nesting in the branches. Apple Bloom decided to try out "pest wranglin'" as her life's calling.
She didn't want to do this. But her friend insisted she help get rid of the unusual feral bats in the orchard using her animal skills. But the most important part of animal handling is knowing when to leave them alone.
One shouldn't tamper with nature.
Nature is a balancing act, a beautiful dance of give and take. Millions of years of evolution have crafted systems and relationships more complex than ponies can begin to understand.
One such system is that of the Vampire Fruit Bat, its target species of tree, the seeds, and a symbiotic relationship between all these plus a gene-altering virus that makes them what they are.
You see, millenia ago these bats were simple fruit eaters, munching through small fruits and spreading the seeds through their digestion. But over time, they acquired a virus that changed their physiology, making them grow bigger, with piercing fangs and a unique gut biome that thrived off the juices of larger fruits.
Large fruited trees like apples and pears evolved to be eaten by megafauna such as horses, but certain tree species benefited from a relationship with strange new bats. The trees changed their reproductive cycles to depend on Fruitvam interference in order to grow into healthy trees. Apples typically have a certain amount of moisture in them, but Pire Apples have an extremely high juice content due to their relationship with Fruitvam bats.
The bats are attracted to fruit with the highest juice content, which their virus-evolved bodies demand. The seeds pass through the bats' gut and are then laid in nutrient-rich guano (bat manure), which exponentially increases the seeds' growing capacity. While the juicy fruit attracts the bats, it is not as good for nourishing the seeds, so the apple tree depends as much on the bats as they do the tree.
The trip through the bat digestive system changes the seeds into more robust, high-yield trees that produce extremely juicy apples. The best cider is pressed from an orchard with a healthy bat population, even though they intimidate farmers at first by devouring their crops. If juices and cider products are a staple export, it's worth it to establish the bats as part of your land management.
Unfortunately, not everyone understands or cares about the balance of nature. You can try to eradicate them, but you must be very careful when doing so.
Bats carry many diseases, but Vampire Fruit Bats carry a particularly virulent condition that defines their life and environment. To the bats, the Vamprus is part of them, and they would not exist without it. They are not mere hosts to a virus, but invaluable partners with mutual benefit.
Fruitvams are born with vamprus, but they still secrete it in their saliva. This is a holdover from when it was a harmful, rabies-like virus that spread through bats biting each other. It does have some effect on their mind, drawing them to seek out juice-rich fruits at the height of ripeness, but this is what the food chain needs, so it is no longer a harmful behavior. They are not aggressive, and have no desire to bite living creatures, bats or otherwise.
However, if one handles a Vampire Fruit Bat with bare hooves, or harasses a nest, they will fight back. Ponies who have been bitten usually escape unscathed, as they are not the definitive host of the Vamprus virus. Those who do develop symptoms, however, need swift treatment or changes become permanent. After the virus leaves their systems, afflicted ponies will no longer be controlled by their desire to drink from apples' flesh, but they will always have a hunger for it.
Some ponies who tangled with bats can be so mildly affected they never even realized they were infected, with no indication save for minor changes... and an insatiable desire for cider.