Author's Note
I wrote this one a long time ago. It's pretty stupid. 
A Harmless Prank
“Yoo-hoo! Rainbow Dash!” Rainbow looked below her. There, stood Rarity and Twilight. Dash said something to the weather ponies she was with, and flew down to her friends.
“Hey guys, come to see us prepare for the storm?” Rainbow Dash said. “It's going to be the longest one yet. Two whole days! 42 hours straight!” Rainbow spoke with excitement in her voice. She always enjoyed working with storm clouds.
“Actually,” Twilight said. “We were wondering if you'd be able to spend those two days with us in the castle. Spike’s in Canterlot, and it's been awhile since all six of us hung out together,” Twilight smiled as she spoke, obviously eager for Rainbow's answer. “Besides, it’d give you sometime to get to know Starlight better.”
Rainbow nodded. “Sure, i’d love to, Wonderbolt practice is cancelled anyway, what time should I come over?”
“Anytime is good, just bring what you need for the next two days!” Twilight and Rarity turned around and walked off, as Dash flew to her house to get her things.
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Rainbow knocked on the door to the castle. She heard a ‘come in’ from inside, and opened the door. As she walked in, she saw Fluttershy, Rarity, and Starlight all talking to each other, and Twilight in the other room. Pinkie Pie jumped out from behind the door, exclaiming: “boo”. Although Dash didn’t jump, she still looked around to see if anyone saw her get scared.
“You got the… you know what?” Rainbow whispered. Pinkie nodded energetically, and opened her bag, revealing a plastic cooking bowl. “Good. Now hide it.” Rainbow made an evil grin.
“So,” Pinkie said in an overly dramatized tone. “Who’s it gonna be?” She rubbed her hooves together like a movie villain.
“Haven't decided yet,” Dash said looking amongst her friends. “Hmmmm… I guess we’ll know when we know.” She put her bag down next to Pinkie’s. “Just try not to arouse suspicion. Don't want to ruin the surprise.”
Pinkie nodded ludicrously and skipped off. “Rainbow! I didn't see you come in!” Twilight said, walking in the room. She was levitating a batch of cookies, and offered them to Fluttershy, while pulling them away from Pinkie’s sweeping hoof, and also managing to keep eye contact with Rainbow Dash.
“Yea, sorry I'm a bit late. Is everyone here?”
“Everyone but AJ, but she told me she'd be a bit late.”
“Cool, I assume you've got both days planned?” Dash asked, glancing a look at Pinkie (who had fallen on the floor after being rejected of the cookies) and winked. Pinkie stared for a moment, then winked back.
Twilight nodded, but before she could reply, the room filled with a bright light, but only for a fraction of a second. It was followed by a loud boom, and then rain pouring down. The storm had started. “Oh, I hope Applejack is alright,” Fluttershy said in a worried tone.
“I’m sure she's fine. It just started, and she should be here any second now,” Twilight said, moving the girl’s bags into the bedroom.
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Applejack burst into the Castle, without knocking, covered in mud, and soaking wet. Shivering, she put her bag on the floor, quickly said ‘hi’ to her friends and dried herself off with a towel. She then came back into the room where all of her friends were, and began to chat, as she typically did in these cases.
The storm went on, and so did the evening. Eventually, the ponies were tried, and decided that perhaps an all-nighter wasn't a good option if they were going to be hanging out the next day as well.
“Heh,” Fluttershy giggled, “let's hope this night isn't as bad as the last time we did this. I'm not a fan of smoke monsters.” The girls laughed at the recollection of the Tantibus. Something about the bad times, it not being so bad now, just made them laugh.
As the lights dimmed, and the last ‘goodnights’ dwindled to silence, Pinkie and Dash silently crawled out of bed, grabbed Pinkie’s bag, and snuck into the Kitchen. “Oh man, this is gonna be great!” Rainbow said, giddy with anticipation. Pinkie filled the bowl with sink water, warm, of course.
“So…. AJ, right?” She asked for confirmation. Dash nodded, smirking a sinister grin.
When the bowl was almost full, Dash and Pinkie carefully brought it back into the room. “You think this is really going to work?” Pinkie asked quietly.
“Only one way to find out,” Dash whispered, holding back laughter. She raised the bowl to Applejack’s hoof, which was, luckily for Dash, already off the bed. At first there was silence. Then disappointment in Dash and Pinkie. Then, the faintest sound,
fffffffffffffffffffffffffffffffffffffffffffft
Dash’s face lit up. Pinkie let out a snort of laughter, in celebration of a successful prank, and Dash quickly covered her mouth. The two hid the bowl under Dash’s bed, and the swiftly got under the covers before anyone woke up.
Dash squinted her eyes to mask her consciousness while still being able to see how Applejack reacted when she woke up. It took less than a minute before she did.
Applejack woke up, eyes wide open. She looked under the covers, and let out a slightly audible gasp. She looked around to see if anyone else was awake. She crept out of bed and tip-toed to where Rarity was sleeping.
“R…Rarity” Applejack whispered in an odd tone.”
Was she?
No.
Rainbow heard a ‘sniff’ and a ‘hic’.
“No way. Applejack doesn't cry, she never cries. Not in a sad way, that is.” Dash thought
“Rarity…” Rainbow Dash could hear AJ’s broken voice. It was unnaturally high pitched, and distorted. Just that one word was so broken, it caused Rainbow’s smile to fade away immediately.
“Rarity!” Applejack’s broken voice whispered. This time, she shook the sleeping unicorn a bit. Rarity woke up slowly.
“Applejack? What’s going on?”
“I… I…” Dash could hear the tears desperately trying to push themselves out of Applejack’s eyes. She could hear the lump the the throat getting larger. She realized that she may have made a mistake.
Rarity sniffed the air. “Oh. I see,” she said, sighing. “Did you tell Twilight?”
Rainbow could see AJ shake her head in the dark. “I don’t want to tell her,” the broken voice said. “I don't want to tell her I did it again…” the broken voice cut deep in Rainbow’s side. She felt bad.
Rarity hushed AJ. “I'll run you a bath. Shh. It's okay dear.” The two walked out of the bedroom, while Applejack wheezed and hyperventilated in her uncharacteristic voice.
Rainbow’s throat was stabbed with regret.
Fluttershy let out a small cough to show she was awake. Starlight did too. Everyone looked up to see everyone looking up.
“I can't BELIEVE you Rainbow Dash!” Twilight yelled, seeing her awake. Everyone jumped at the sudden loudness.
“It was just a prank, I thought she'd be fine with it. She’s been fine with pranks before,” Dash rebutted.
“ Dash!” Twilight yelled with blatant frustration. “Applejack has a literal medical condition! She takes medication to stop her from doing that! That's why she almost never comes to one of these! She's afraid! And the one time I can drag her out to her out with us, you and Pinkie ruin it! So thanks a lot!”
Dash snapped back, “How was I supposed to know?”
“The medication she takes everyday, the trauma of her parents’ deaths, there fact that she never comes to these sleepovers! She's only been to, four. Yes, I've counted!”
“What medication?”
Twilight pointed to an orange medicine bottle by Applejack’s bag. It was labeled Trospium Chloride
“Yea? Well y-”
Rainbow was cut off by Fluttershy shushing. “They're coming back!” everyone pretended to be asleep again, but not before Twilight gave Dash and Pinkie an evil state one last time.
Applejack has stopped crying, and was being escorted back to her bed by Rarity. “Alright, there. I cleaned the sheets, so Twilight won't have to know,” Rarity whispered, giving Twilight a quick glance.
“Rarity… I did take my medicine,” AJ said in a still somewhat cracked tone.
Rarity trotted back to her own bed. “I know, I know.” She looked at Pinkie, then at Dash. “I know”
