Sunset stood facing Flash Sentry's home, looking at the "For Sale" sign. She remembered how no one, students, CHS administrators, or even Flash's few friends outside of school, had seemed to care that he had disappeared one day with no explanation at all.
There was something she wasn't seeing. Some piece of the puzzle...
Sunset noticed a shadow on the ground, cast by something behind her. She dropped her Friendship Journal as she spun around. "Caught you!" she shouted, tackling a mysterious figure.
"Oof!" the green-haired girl complained from beneath Sunset. "This shouldn't be happening!"
"What do you mean, shouldn't be happening?" Sunset poked the girl's stomach hard. "What do you know about Flash Sentry? Why are you skulking around his front door like a suspicious character? Tell me everything!"
"Sunset!" the girl whined. "YOU were the one skulking around his front door just now like a suspicious whatever. And you know what else is suspicious? Even more suspicious?"
"What?" Sunset demanded.
"That you even know who Flash Sentry is."
"He's...a guy. I dated him for three whole years. It's no wonder I...kind of remember him?"
"Oh, good. You don't care about him either. Not really."
"I warn you!" Sunset hissed, "I was a school-oppressing bully for three and a half years, and I've still got my skills." She pressed two knuckles into the other girl's back. "I can give you the knuckles, I can swirly you...I've even been studying how to waterboard. By the time I'm done with you, you'll WISH you were an Equestria-hating terrorist! You'll tell me everything I want to know! You'll rat out your own mother just to make me stop!"
~~ * * * ~~
With her hands tied behind her back, and her face pressed against the inside of Flash Sentry's toilet bowl, the girl burbled and cried. "I confess! I confess! I did it! Just please stop being so horrible to me!"
"How did you do it?" Sunset shouted. "HOW? I need to know EVERYTHING!"
Wallflower gasped. "I use a...memory stealing stone. It's in my backpack. All I have to do is touch it, and I can make anyone's memory of something go away. It's really that simple."
"Sounds...like a story," Sunset growled. "Maybe it's even true. Or maybe it isn't. But if it IS true...why did you do it? And why don't people care about where Flash is?"
Wallflower whined, "I told everyone to forget that they ever cared about Flash Sentry. So they kind of know that he exists...kind of? But he doesn't matter to them. He's like a nothing to them."
"Is that SO? And WHY would you have done that? Huh? Huh? Better remember soon, if you ever want to breathe AIR again." Sunset flushed the toilet, hard.
When the flush's echoing rumble died down, Wallflower said, "It's because...people saw him differently from me. They saw HIM, and they thought he was cool. They liked him. And he was...kind of cute. But a guy like that would never be interested in a girl like me. It isn't even worth trying."
"You're pathetic! And a coward. And you know what else is wrong with you? You need some bucking self-respect. Instead of assuming he wouldn't like you, instead of using some magical stone on him that probably doesn't really exist because you're probably full of shit anyway, why don't you try just asking some guys OUT for once. I'm sure some guy would say yes. I mean, if guys are what you're into."
Wallflower sighed. "I DID try asking guys out. I asked out all the guys at CHS. I asked out some guys at the mall. And you know what happened?"
"They said yes?"
"No! It was like no one even cared. It was like they hardly even noticed me. So finally I decided I wanted to get back at them. I wanted to get back at them all! Some guy would FINALLY buy me a Slurp-ee, even if I had to do it the long, hard way."
"Wallflower!" Sunset shouted. "The long...hard...you had sex with a guy for a Slurp-ee? Because if you put out, a guy should at least buy you--"
"No, you bullying moron!" Wallflower breathed heavily, clenching her fists. "I picked out a guy, made everyone in the whole world forget they cared about him, made him forget where he lived, and I sold him human trafficker style! Now he's a slave in a royal harem, in another world where magical horses really like back rubs done with real hands or something."
"What?" Sunset said. "Celestia would NEVER."
"Our principal has nothing to do with it. I sold him to 'Magical Princess Lyrabean,' or whatever her name is, in Magical Pony World AU-3509. There are LOTS of AUs where magical pony princesses will pay in gold and gems for human slaves. Especially if they're the cute boys who rejected me, before I turned evil! Those bastards!"
"Wallflower," Sunset said.
"What? I'm horrible? Enslaving humans is wrong? Cute boys who ignored me and made me feel bad shouldn't be shackled in cold, hard iron, sold to another world, and forced to spend their days and nights learning how to pleasure pony princesses with their p-p-penitence?" Wallflower breathed deeply, her chest rising and falling. "Well, I don't care what you think about me! I know you think I'm ugly and gross and horrible and evil!"
Sunset said, "Evil, maybe." She barely kept herself from adding, I never realized just how sexy an evil green haired girl could be, talking about chaining up boys and turning them into erotic slaves. To serve ponies.
Instead, Sunset said, "I don't think you're completely horrible. I just think you've...made some mistakes. But it isn't too late to change your ways. You can become a better person. Maybe we can even get the boys back. We can rescue them!"
"I sold some of those boys to the Griffon Dimension, for lunch."
"There's nothing wrong with making snobby boys work a few shifts as waiters--"
"Griffons eat meat, Sunset. FOR LUNCH."
Sunset gasped.
"And you know what else?" Wallflower wriggled and writhed, stretching her bonds a little farther. "Think I've got it....YES! I did lie about one little thing. The magic stone isn't in my backpack."
I would say that was the last thing Sunset remembered about that day...but Sunset was already forgetting. Wallflower wasn't bluffing.
"Forget you don't want to untie me. Now untie me."
Sunset's eyes went vague and confused. "Ok, Wallflower."
"And you know what else, you stupid bully? I know how to break that stupid portal you use to go back and forth between here and your pony world. When you were fighting with Princess Twilight the night of the Fall Formal, you told most of the school how to break the portal with a sledgehammer. You moron. Now forget you don't want me to break the portal. Forget that stupid pony world and everything about it."
"Huh?"
"Never mind. Untie me NOW. You don't remember ANY reason not to untie me, and you remember every reason you SHOULD. Because you can still remember that bullying me is wrong and you should be ashamed. But you can't remember anything about any memory stealing stone. Which isn't a real thing, and you've never heard of it."
"Um...ok. I'm so sorry. What got into me? Was I bullying you? I'm so sorry!"
"Just untie me!"
Sunset untied the green-haired girl.
Wallflower left the house while Sunset was still sitting on the floor, stunned and confused.
As Wallflower walked across the front lawn, she stopped briefly to pick up the Friendship Journal. "Oh, Sunset's diary. How cute. I think I'll read it, so I can learn everything about your life that you can't even remember anymore. Or maybe I'll just throw it in the trash unread. Either way, that's what a bully like you deserves."
~~ * * * ~~
In Wallflower's locker at school, Sunset's Friendship Journal buzzed and glowed. A new message had appeared, from Princess Twilight in the Pony Dimension.
Sunset, the pony world's Flash Sentry recently went missing, but we found out what happened to him. He went to visit a town called Hope Hollow, where a malfunctioning Rainbow Generator ate up everyone's hope, enthusiasm, and caring about anything or anyone. Also sucked up all the colors in town, and ponies' ability to smell tangerines, I don't know why.
Unfortunately, Flash was especially vulnerable to the machine. Just spending a few hours near it was enough to make him stop caring about anything at all. He didn't even care to step out of the way of a speeding wagon, so he got smashed up badly enough that he's in a nearby town's hospital. (Hope Hollow General didn't care enough to bother to admit him, so he just lay unmoving on the lobby floor for days.)
That's why Flash got in trouble at his job as a Crystal Empire Royal Guard: he was AWOL from work for days and days, and nopony knew why.
To warn other ponies not to let the same thing happen to them, Equestrian Educational Films is going to make a 'based on a true story' movie called "Rainbow Roadtrip." In the movie, some ponies go to visit a town like Flash Sentry did. But instead of going AWOL in the hospital, the visitors use friendship magic to defeat a broken Rainbow Generator before it makes them all stop caring about things too. I MIGHT have suggested to the scriptwriters that if they want to, they could base the movie's main characters on some of my friends.
I guess something like the broken Rainbow Generator might be what happened to your Flash Sentry, too. What's your world's equivalent of the misbehaving Rainbow Generator? Is it scrolling through FaceHoof until you forget to eat and sleep? Is it forgetting to go outside, and appreciate real things? Is it eating only factory made food extruded from machines, until you miss out on some vital nutrient that you need to think and feel properly?
I really do wonder about FaceHoof. Spike was telling me the other day, he noticed when we were both visiting the human world that some humans seem to get addicted to it. It's like they get hypnotized.
Spike thinks an evil hacker could use FaceHoof to confuse and brainwash people into forgetting who and what they really care about. But I hope Spike is just being a silly little kid about that.
I'm eager to learn how you solved (or solve) the Flash Sentry problem on your end, too!
Hugs, Twilight
~~ * * * ~~
Buried deep underground, in a garbage dump many miles away from Canterlot High School, a book vibrated.
Sunset?
Sunset?
What happened to you?
Why aren't you answering? Why don't you EVER answer my letters anymore?
Sunset! Where are you? And why isn't the Mirror Portal to Canterlot High School working any more? I feel like something must be terribly wrong, but I don't know what!
Sunset! I don't know what happened to you, but I'll never forget you, or the important lessons about friendship you helped me learn! 
~~ * * * ~~
Sunset Shimmer woke up slowly, with a heart monitor and other machines beeping nearby. She tried to lift her arm to wipe the crusties out of her eyes...but she could hardly move.
"Sunset!" Twilight Sparkle shouted. "You're awake!"
"Nn," Sunset grunted. "Rrg."
"If you can hear me...grunt once for yes, and twice for no!"
Sunset cleared her throat. She whispered, "For fuck's sake, I can hear you. But what happened?"
"You were found unconscious, with a ballpoint pen that had been chewed into pieces. The doctors think you tried to eat the pen for some reason--"
"I was nervous. Nervous chewing. What, like YOU'VE never been so tense that you chewed on something?"
"--and you consumed an almost lethally high dose of ink."
"What?"
"You poisoned yourself. Don't you know you're NOT supposed to suck all the ink out of those things and swallow it?"
"What."
"You drank so much ink, you got high and hallucinated."
"Is that even a thing? I can't believe that can really happen. Wouldn't we have heard about it? Some kind of warning?"
"The authorities have been trying to keep ink poisoning a secret. Something about not wanting every kid in the country to try to get high on ink themselves, at least until all the 'bad trip' pens can be recalled first."
"That's crazy."
"Is it, though?" Twilight asked. "What do YOU think happened? Do all your memories of the last few days really make sense? Or do they make a lot more sense as a series of near death, drug crazed hallucinations?"
Twilight took a deep breath. "Or do you think all your hallucinations really happened, and what I'M telling you is crazy?"
Sunset thought for a minute. It wasn't impossible that Flash Sentry could have disappeared for some reason. Running away from home, or kidnapped...but, ok, probably not that crazy story Sunset remembered Wallflower telling, about what she'd done to him.
Wallflower said she'd sold a lot of missing boys into...some kind of slavery, somewhere? But sold them how, and to whom? Who would want to buy them? Was it aliens? Or maybe evil Caneighdians?
Sunset shook her head. What she could remember of the story didn't make any sense. It was like a jigsaw puzzle with more than half of the pieces missing. It was just loony.
But that everyone would just stop caring about their friend Flash, and not wonder why he was missing, and not worry about him at all? THAT was the most unbelievable part.
"Ok," Sunset said. "I suppose you're right. The things that I thought happened...they make no sense. I guess I DID get ink poisoning, and weird hallucinations. That explains a lot."
"Good!" Twilight said. "So you're getting better! I'm so happy. Because a FEW people, a VERY few people...they just never snap out of it. They're lost in a maze of delusions forever." She smiled hopefully. "But that's not you! You're fine!"
Sunset blinked. "One thing, though."
"Yes?" Twilight asked.
"What happened to Flash Sentry?"
Twilight's eyes narrowed. "Who's that?"
"Flash Sentry? The guy who...um...well...I think I dated him for three years. Plays guitar, drives a sports car, kind of cute in a really generic way...come on! Isn't any of that ringing a bell?"
Twilight shook her head. "Sunset. I'm sorry I have to tell you this...but I don't think this Flash Sentry is real."
Sunset tried to scream, but it came out more like a weak croak. "No."
Through the doorway, Sunset thought she saw a green-haired girl with a cruel look in her eyes. But a moment later, the girl was gone, as if she'd never been there at all.
"What was I saying?" Sunset murmured. "I forgot."
Twilight scratched her head. "Something about...I don't know, some guy?"
Sunset snorted. "It probably doesn't matter. Someone told me once...guys are like goldfish. If everything goes down the toilet, you can always go to the mall and get another one."
Author's Note
This story WOULD have been loosely based on a remark by FanOfMostEverything, but I ended up changing everything until it wasn't that idea anymore. (Or is that really true?)
FoME's original remark was:
'Horrible idea: OC haremfic, except it's a canon character with a harem of OCs.'
