(The Prompt: Fluttershy’s vampirism awakens.)
Applejack trotted casually down the lane toward Fluttershy's cottage. It was warm and pleasant out, a nice late summer day in Ponyville. Only a few clouds dotted the sky, just enough to break up the endless blue, and the temperature was just under being too hot. By all accounts, this was the kind of day that would usually put Applejack in a bright and cheery mood.
Not today, however. Her saddlebags contained a few apples, all drained near dry of their juice. Unsellable, of course, but more worrying for other reasons. The sunlight seemed to dim slightly as Applejack approached the lonely cottage, way out in the outskirts of Ponyville. Times had been changing, lately. The animals around the cottage now included nearly half the vampire fruit bats that used to stay in the sanctuary on Sweet Apple Acres. Fluttershy couldn't convince the bats to leave, but they seemed comfortable enough there that she hadn't tried overly hard.
Applejack knocked lightly on the door. A few moments passed, but then a quiet, slightly raspy voice called out from the other side. "Oh, no visitors today! I um, don't mean to seem rude, but--"
"It's me, Sugarcube. C'mon an' open up."
The lock, fairly newly installed, clacked loudly as it was undone, and then the door opened. Applejack stepped quickly inside, and jumped a bit as the door closed behind her. She turned around to face her friend, Fluttershy. Fluttershy's eyes were strangely red, and her lips failed to completely hide the pointed fangs she'd grown. Fluttershy's head dipped a little as she saw Applejack's eyes. "It's... happening again, I'm sorry about your apples, I... I can't help it, some nights."
Applejack opened her saddlebags and pulled out the batch of apples. There were only five, and she set them down on the coffee table with a slight squishing noise. "Y'had five this time, Fluttershy. Now don't you worry about payin' for-"
"But I have to pay for them!" Fluttershy swooped forward, and wrapped her forelegs around Applejack tightly. "I can't eat your apples and just not pay for it, Applejack."
Applejack pulled back slightly, but didn't bother fighting to get away from her friend. "Come on now, Fluttershy. Five apples ain't a big thing between friends."
Fluttershy nodded, and nuzzled slowly against Applejack's neck, breathing in through her nose as she did. Applejack gently but firmly pushed her away, and Fluttershy resisted for only a second or two before letting go and flying several feet away with her eyes widening. "Oh! I'm so sorry, Applejack, I can't help myself. Please, we need to go to Twilight about-"
"We ain't goin' to Twilight, Sugarcube. Look, I know she might have some spell or somethin', but every time she's tried with this she's just gone an' made it worse. First vampire fruit bats were bad enough, but then her magic made you a vampire pony bat or somethin', and then tryin' to fix you made you... well, y'know. Like this. I'm not lettin' her make more of a mess of things than she already has."
Fluttershy landed on the floor, turning her head aside and looking down and away. "But... the first time took a month, and then three weeks, and..."
"And now it's been two weeks an' we're doin' this again. Dont' you worry, I'm bettin' it'll slow down come the end of harvest season."
Fluttershy sighed, and walked over to her coinpurse, fishing out a few bits and setting them down on the table for Applejack. "... There, that pays for the apples."
Applejack picked up the bits and stowed them in her saddlebags, and then looked to Fluttershy. "And th' other part?"
She seemed to shrink away from Applejack. "Can't I just keep paying for apples? I have the money for them, if I don't buy special food for Angel."
"An' risk lettin' this thing set in more than it has already? You know th' longer you go without doin' this the hungrier an' battier you get."
Fluttershy took a step toward Applejack, her eyes wide and staring at the other mare's neck. "But... but I remember doing it now, and it's... so awkward, and strange, and I... I hate being a vampire pony..."
Applejack set her hooves on the floor, willing herself as hard as she could to stay put. There was a sort of gleam in her friend's eyes that set off deep-seated instincts. Ponies, as a rule, didn't generally like predator animals. "It's my fault things are gettin' this sour. Don't you blame yourself, Sugarcube."
Fluttershy finally reached Applejack, and reared up slightly, resting her forelegs over Applejack's withers as she leaned in. She sniffed Applejack's neck, as her eyes glazed over. "It's... so strange though."
Applejack set her jaw, and forced herself to stay standing as her fur set on end. She stayed quiet. There was a price to be paid for keeping her friend now that she'd made the mistake of getting this magic on her, and Applejack was more than willing to pay any price to keep her friends around.
Fluttershy opened her mouth, and then pressed forward, sinking her fangs into Applejack's neck. The other mare jumped at the sudden pain, but held still as best she could. The pain faded quickly, as always, and there was just a soothing warmth from Fluttershy holding on to her, and a spreading calm and almost pleasant numbness from the bite. Applejack's entire body relaxed as Fluttershy drank from her, even as her head grew foggy and her legs shook.
A minute or two passed, neither pony could keep track of time, before Fluttershy pulled away with a gasp, and backpeddled several feet, until she bumped into a wall. She shuddered and whimpered as her fanged teeth retracted to the smallish little nubs they were before, barely any longer or sharper than her other teeth. Her eyes lost the red gleam, and she finally felt sated.
Fluttershy sank to the floor, with tears welling up in her eyes. Applejack stood still a moment, before turning to look at herself in a nearby mirror. As usual, she wasn't bleeding even after that. She walked over to her friend, and lay down beside her, hugging her close. Fluttershy sniffled and held tightly to Applejack.
Applejack felt terribly drained. Every time they did this, she felt a little worse after. But it was still worth it, to keep her friend healthy. Fluttershy sobbed against her coat, and Applejack felt lower than a snake, having done this to one of her best friends. Still, what was done was done, and there was no reason to go on beating herself up about it.
It was nearly an hour later that Applejack managed to leave the small cottage. Fluttershy had mostly recovered, and after a bit of a late dinner, Applejack was feeling better despite her blood loss. Applejack waved to Fluttershy as she trotted down the path, away from the cottage. She watched as Fluttershy closed the door.
Applejack turned to face forward. She ran her tongue along her upper teeth, feeling the small, pointed canines that suddenly seemed so pronounced.
She might have to go to Twilight after all.