A/N I had this idea a couple hours ago and decided to make a super-short fic out of it.
It was a cool fall evening in Ponyville, and Applejack had just finished her work for the day.
"Whew! Nothin' like an honest day's work. Ah think ah'll head back to the homestead and see if Granny Smith needs any help with supper." AJ said to herself. She turned and headed back to the house. She got to the front door, opened it, and walked into the family room. To her surprise, Fluttershy was in the center of the room playing with Applebloom.
"Fluttershy, what a nice surprise! Are ya here for supper?" She asked.
"Um, no… actually Applejack, I was wondering if I could have a word. Um, privately. But only if that's okay with you…" She said in her usual timid manner.
"Ain't nothin' major. We can go upstairs to my room." Applejack offered.
"That's good. Thank you." Fluttershy replied.
"Follow me." Applejack said, walking towards the staircase. They climbed the worn stairs in silence, but once they reached the top Applejack looked over her shoulder back at Fluttershy and asked,
"So what is it ya wanted to talk about sugarcube?"
"Well, I've been having… strange issues…" Fluttershy responded, her voice just above a whisper.
"What kind of issues?" Applejack asked with a look of confusion upon her face. She opened the door to her room and led Fluttershy inside, shutting the door behind them.
"Well… you remember the incident with the vampire fruit bats from a while ago, right?" Fluttershy asked.
"Yeah, but Twi said she got everything back to normal, and you've looked fit as a fiddle since then." Applejack responded.
"I don't know, every night since then I've been having these strange… feelings. Like I haven't been quite myself." Fluttershy said, unsure of herself.
"Well what kind of feelin's are ya feelin'?" AJ asked.
"I… don't know. I just get so… thirsty. And I'll drink and drink and drink but I still feel so thirsty." Fluttershy said, tears brimming in her eyes.
"Now now sugarcube, no need to get upset with yourself. Ah'm sure it's nothing Twilight can't fix. Let's go see her and see if we can't get you fixed up. Sound good to you?" Applejack said consolingly.
"NO!" Fluttershy cried, tears trailing down her cheeks now.
"Woah there Flutters! Calm down now… it's gonna be alright…" Applejack cooed.
"It's not alright…" Fluttershy said. Her voice, the smallest whisper; her eyes boring into AJ's.
"I'm so...thirsty…" Fluttershy whispered, deadly calm. Just then, the moon rose above the horizon and light streamed through the far window. Applejack watched, terrified, as the moonlight struck the kind, quiet, loving pony in front of her. She watched as the light shone off of her fangs, illuminating her mottled, batlike wings; her huge, pointed ears; and her dead, blood-red eyes. Applejack, frozen in horror, could do nothing as the now-transformed Flutterbat pounced on her and plunged her huge, white fangs into her neck. Applejack screamed in agony as every drop of blood was drained from her body. Once Flutterbat had finished her meal, she let the orange mare's lifeless body fall to the floor and took flight, smashed through the window, and flew into the night beyond.
"I'm...still...THIRSTY!"