PROMPT: 
>anon is rewarded for his investigations with a cutie-mark for his talents in cutie-mark forensics.
>he turns his talents towards understanding his own mark.
>it's a mystery how he even got it, surely a human couldn't...
>he reaches the Earth-shattering conclusion: He truly is a filly now. There is nothing that can turn him back.

STORY:
>I am Anon. 
>Horsefucker extaordinaire
>Private detective in a town that hardly ever needs me.
>But I have no other way of earning money in this town, and ponies will pay a fortune for me to do off the books illegal work.
>One day, Twonkle Sponkle walks into my office with a very certain look on her face
"Can I help you, Spankle?"
>"I told you never to call me that, Anon. Anyway, I have a job that I need you for."
"Shoot."
>"I need you to investigate a group of schoolchildren."
"Twilight, I don't do kids."
>I inwardly chuckled at my joke that Twank clearly didn't get
>"I know you don't, but this isn't even illegal. Besides changing and creating some documents, which I, as a princess, have the ability and legal right to do, it's completely harmless."
>I contemplated this for a bit, rubbing my chin in thought.
"Alright, fine. What's the 'sitch?"
>"I need you to investigate the Cutie Mark Crusaders."
"Ok... Why?"
>"I'm not convinced."
"Convinced about what?"
>"Their cutie marks! This is the first time in recorded history that three filly's that are not blood related, to receive almost identical cutie marks! It makes no sense!"
"So you want me to follow them? Question them?"
>"Well... I've been researching a spell that I've been wanting to try, so..."
"Hold it. What spell is this."
>"It's a transformation spell. Basically, it can turn a being of one species into that of another and will let me chose the age of that being when I cast it."
"Then why not cast an aging spell on yourself"
>"Because the spell is semi-permanent. If I age myself down, my magic reserves will not be enough to bring me back."
"I see... So you want me to infiltrate the school as a pony and try to figure out what the Cute Mark Crusaders are up to?"
>She nodded.
>"Precisely."
>I thought for a few seconds.
"Okay, I accept. I hope you don't mind me charging a little more than usual, seeing as this is a very risky mission."
>"Absolutely."
>I stood in the center of the room as Twank Bank charged up her horn.
>A beam of purple magic shot forth and struck me in the chest, immediately triggering changes.
>I felt myself began to shrink and my bones shift to different positions.
>Besides the growth of fur and the loss of feeling in my fingers and dick, not much else changed.
>Wait, what.
>Why couldn't I feel my dick.
>I looked down only to watch as by testicles and precious rod disappeared inside my body.
>Soon after I looked down, my dick had completely disappeared and the changes were complete.
>I looked up at Purple Smart who had a proud look on her face.
"What the ff fffb-b-buck, Princess Dumbass! Why am I a filly!?"
>My voice was squeaky and high, just like that of a little girls.
>"Oh, about that. I only had one other "Pony of Reference" to use, and that was me. I essentially cast a transformation spell to make you look exactly like me, a cosmetic spell to change your coat and mane, then an age spell to change your age"
>She looked at me, somehow proud of what she had done.
>At least it wasn't permanent.
"Whatever, Fleshlight Sporkle, you just jacked up the price for this job by double."
>"Whatever is necessary. I took the liberty of enrolling you at the school the CMC are at and your school day should be starting in half an hour. I'll teleport you there, wouldn't want you to be late!"
>Before I could protest, she shot me with another beam of magic and we both appeared outside the school.
>I tried to insult her, but she teleported away again, leaving me gawking at nothing.
>I glanced at my body, taking in the changes that the Purple Pony Princess had made to me.
>I had a forest green coat and a black mane, just like my normal hair.
>I scoffed at what had happened and made my way to the classroom. 
>The faster I got through this, the better.
>The school bell rang and I made my way to an open seat at the back of the class.
>It dawned on me that Twibright had assumed that I knew what the CMC looked like, which, in fact, I did not.
>I looked at the door of the classroom as it began to fill with young ponies of all colours and types.
>Eventually, three ponies walked in with the same cutie mark on their flank, just as the purple idiot had described.
>Unfortunately for me, they decided to sit at the front of the class, while I had chosen to sit at the back.
>My old habits deceive me once more.
>Class was boring, but it was over sooner than I thought, and recess began.
>Out in the school yard, I saw that the three ponies I was after were sitting together at a table and were eating their food quietly.
>I approached them, not concerned about acting like a little kid. After all, I used to be part of a special task force of very young looking cops who infiltrated high schools.
"How do you do, fellow kids?"
>They stared at me.
>"What?" The white one looked at her friends and shrugged.
"I was told that you three were helping young ponies find their cutie mark, and as you can see, I don't have any branding yet."
>"Branding? I uh... Have no idea what ya mean by "branding", but if yer talkin' about yer cutie mark, Ah think we can help ya!" The yellow one said.
>"Ah'm Applebloom," She pointed to herself."This is Sweetiebelle," She pointed to the white one that talked before. "And this is Scootaloo!" She pointed to the last filly who waved excitedly.
>"We'd be happy to help you find your cutie mark!"
"Well, I'm more interested in how you got yours. Why don't you tell me?"

__________

>"... And that's how we got our cutie mark, all at the same time."
>I hated to admit it, but the story checked out.
>Admittedly, I didn't know exactly how cutie marks worked, but from what I had gathered from living here for a while, their story was no more unbelievable than the rest.
>"So, what do you think you're good at?"
"Well, I always had a knack for..."
>Don't say being a private investigator, dumbass.
"Uh... Skating! I sure do love to uh... Kickflip and stuff, yo!"
>Again, the yellow one named Applebloom stared at me.
>"Wow, really?!" Scootaloo piped up. "I am like, the best scooter rider in Ponyville and I don't even have a cutiemark for it!" She squealed happily.
"Well, that is the bomb diggity!" 
>I am a master of disguise.
"Why don't you teach me to ride a scooter!"
>"Sweet!" She said as the school bell rang. "I'll meet you after school!"

>The end of school finally came and I walked outside to see Scootaloo waiting with two scooters nearby.
>Execute phase one of plan "Wet Faggot"
"Hey Scootaloo!"
>"Hey, uh... I don't think I ever got your name."
>Shit, think quick.
"Green, uh... Glass! Yes!"
>"OK, Green Glass, you ready to ride?"
"You bet it, mother-bucker!"
>"Woah, Glass... I mean, I'm a cool pony, but language like that... Didn't your mum ever tell you what that means?"
>To be honest, I thought it was the equivalent of "fuck". 
>Actually, that makes sense.
"Uh, sorry. Anyway, I thought maybe we could ride the scooters around Ponyville Park? They got a cool pond there!"
>"Sure!"

>It didn't take long to get used to riding a scooter as a pony, but I wasn't anywhere near as good as it as I led on. Especially not with my forelimbs now being as long as the back ones.
>Actually, maybe this would play to my advantage.
"Woah, WOAH!"
>I faked a fall and splashed into the pond, showering the orange pegasus with water.
>I pulled myself out of the pond and comically spurted water out of my mouth, directly onto Scootaloo's cutie mark.
>Nothing...
>Well, I scratch it being painted on. That mark was on there with something other than paint or markers.
>The next day rolled around and I approached the CMC during recess again.
"Sorry about yesterday, Scootaloo. I guess I'm not as good at riding a scooter as I thought."
>"That's fine, Glass! It was fun anyway, even when we got wet!"
>"Yeah, we got wet all the time when we were trying out new things to get our cutie marks!" Sweetiebelle added.
>I inwardly chuckled again.
>"Cutie Mark Crusaders, heeelp!"
>A voice shouted from behind us. We turned to see a purple filly with a golden mane sprinting towards us.
>"What is it, Stawberry?"
>The filly stopped in front of us, panting.
>"I need your help! Somepony's stolen my Wonderbolts collectors cards!"
>"A mystery, eh?"
>A mystery... This was perfect! I could do this! After all, I am Ponyvilles only successful private detective!
>Focus, you're not here to solve the mystery of the missing cards, you're here to solve the mystery of the false cutie marks!
>Although, one little simple mystery couldn't hurt...
>And I'm sure I can use this to my advantage in figuring out the CMC's cutiemark secret.
"We accept!"
>The other three looked at me.
>"Glass, are you sure?"
"Who knows, maybe my talent is solving mysteries!"
>That'll convince them.
>Scootaloo nodded.
>"Okay then, Strawberry Blossom! We accept!"

>"I could have sworn that they were here a few hours ago! I was looking for them to show to my friend, Silver Spoon, when I realized that they were gone!"
>I looked around her room with the CMC, observing the surroundings and checking for clues.
"So did you tell anyone where they were? Did anyone see you take them out at any point?"
>"I don't think so... Only my family, but they've known I had it for years."
>Hmm, It wasn't likely that it was her family. Maybe Silver Spoon, the friend that she was going to show her collection to. It did make sense for her to fake asking to see it, that would eliminate suspicion.
>"Hey, Glass, check this out!" Scootaloo said, looking into the filly's desk.
>I looked at what she was pointing at and saw a thin hair. If only I could take a closer look...
"Hey, is there a magnifying glass around here somewhere?"
>Scootaloo rushed off and was back a few seconds later with a small magnifying glass.
"Thanks"
>I tried to grab at it with my hooves, but it was quite hard to hold.
>"Why don't you use your magic, Glass?" Sweetiebelle asked.
>Magic?
>I looked up and saw a green horn sticking out of my head. 
>How the heck hadn't I noticed that!?
>I guess it did make sense, seeing that Twilight made me to an image of her before changing my looks.
"Uh, I haven't learned how yet."
>"Really? Even Sweetiebelle can use her magic, and she was the last in our class!"
>"Scootaloo!" Applebloom whispered harshly and punched her on the arm with enough force to get the point across.
>"Heh, sorry."
>I didn't care that much, I'd only been like this for a day.
>I settled for using my hooves and looked down at the hair.
>Silver... Just like Silver Spoon's.
"A silver hair..."
>"Silver Spoon!" The three said in unison.
>"Ah knew she hadn't changed!"
"Don't jump to conclusions. Now you said that the only other pony who knew it was here was your family?"
>"Well, only my brother knows it was here. My family knows I have it, but I've only told my brother where I hide it."
"Then that settles it. We question your brother."

"WHERE WERE YOU TWO HOURS AGO!" 
>I shouted in the scared little colt's face.
>He whimpered under the light of the desk lamp.
>"I... Uh, I was... Here! At home!"
"A likely story... So. Who did you tell."
>"T-Tell what?"
"Don't play games with me, kid!"
>"K-kid!? I'm like, a year older than you!"
"Stop changing the subject! Who did you tell! Answer me, who did you tell!"
>"It was... It was Snow Ball! It was... Oh goddess, she'll never go on a date with me now..."

>We ran to school the next day and managed to catch Snow Ball, a blue and, you guessed it, silver maned pegasus before class started.
>"Snow Ball!" Sweetie shouted. "We know you did it!"
>She looked at us nervously, biting her lip.
>"D-Did what?"
"We know you stole Strawberry's card collection! We have a testimony from her brother who admitted to telling you where they were!"
>"Th-That idiot! Uh, I mean..."
"Just admit it, Snow Ball"
>"FINE! I did it, OK?"
>Strawberry stood there, shocked.
>"Snow Ball... You betrayed me! I thought we were friends!"
>"We are, I was... Just... I'm so sorry, Straw, how could I be so stupid..."
>"Why? Why did you do it?"
>"I was... Jealous. She was just always bragging about how great her collection was, and she's not even a fan! I've been trying to collect for years, but she just got lucky! I was gonna give it back today anyway. I really am sorry, Straw. Will you ever forgive me?"
>"Snow, I... I forgive you."
>"Thanks, Straw. Let's go to class and I'll give you back the cards. I'm sorry again."
>The two friends hugged and walked off to class together.
>"Looks like a happy ending!"
"Yep!"
>I smiled before a flash of blinding white light emitted from behind me.
>I turned around to see what it was only to see three filly's staring at me with huge grins on their faces.
>"WE DID IT, WE DID IT! CUTIE MARK CRUSADERS, YAAAY!"
>The three shouted in unison.
"Wh... What are you talking about?"
>"Yer cutiemark, Glass! You got it!"
>Wat.
>I turned my head to look at my flank and saw that both sides were adorned with a brand. A silver handled magnifying glass with a black question mark in the center.
"Ponyfeathers."

"TWILIGHT BUCKING SPARKLE, HOW THE BUCK DO I HAVE A CUTIE MARK!"
>I screamed in the purple faggot's face as she reared back is surprise.
>"A cutie mark?" She said, her face switching into thought mode.
"Yes, Twopple. A cutie mark. Why do I have one."
>"This doesn't make any sense... You shouldn't be able to get a cutie mark!"
"It doesn't matter, anyway. I don't think the cutie mark crusaders have faked their marks at all."
>"What? How can you tell!"
"Well first of all, It's not drawn on. I tested that theory out, and there's no way that it is. Regardless, It's well drawn if drawn at all, and I don't think any of those fillies are skilled enough to draw that perfectly once, let alone re-apply it regularly. Second of all, they helped me get my cutie mark. If the CMC helped /me/, a human who, according to you, "Shouldn't be able to get a cutie mark", then they have absolutely proven the power of their talent."
>"Shit"
"Hey, no fair! If i couldn't swear as a pony, why can you!"
>"Oh, sorry, Anon. That was me. I was tired of you saying such vulgar things, so I made it impossible to say them in case it broke your cover."
"Whatever. Turn me back to normal now. I expect payment still, I did what you wanted."
>"Absolutely." She charged up her horn and shot the beam of magic at me.
>I expected to feel myself growing again, but instead, felt no changes at all.
"Twilight... Why am I still a pony."
>"I- I don't understand... Give me a sec."
>She shot the beam at me again only for nothing to happen.
"Why isn't it working, Tweedle. WHY THE BUCK ISN'T IT WORKING!"
>"I don't know! The "Revert to Normal" spell should be working!"
"Revert to Normal?"
>"That's how it works. It finds your normal form and reverts your body to that form! Only a huge magical event could change that, like if you caused a Rainboom, or if your form was changed again in any way like... Oh crap."
"What. What, Fleshspank, WHAT!?"
>"If your form was changed in anyway like... Getting a cutie mark."
"TWILIGHT YOU BUCKING FAFF- F F... FILLYFOOLER! Well, just cast the transformation spell again and age me up. Simple, right? Do it now."
>"Not exactly..."
>Of course not.
>"When I cast the original spell, I had to use a "Pony of Reference", remember?"
"Yeah?"
>"Well... You're the only human on Equestria, and you aren't exactly... Human anymore. There's nothing /to/ reference."
"You're bucking kidding me."
>"I'm sorry Anon, there's nothing I can do! I mean, maybe I can do some research into other transformation techniques, but I've been searching for others for years!"
"You Mule-hole. What the buck am I gonna do now?"
>"Well, I suggest you keep going to Ponyville Primary. You can't exactly operate a business as what you are now, which is technically a minor... And you are still legally enrolled there."
"What about food, huh? I can't pay for everything without my income!"
>"I- I'll help you out for that, and you can stay in my castle for the time being. There's enough rooms that I don't use."
"Good. Fine, well you better start searching for a cure, and sooner rather than later. Being a pony is uncomfortable enough, let alone being a filly pony."
>"Don't worry, Anon. I'll figure something out."
>Buck you, TwinkleSpit. 

>Two weeks later.
>I still haven't forgiven Fleshrend Faggotron for turning me into a pony permanently.
>Hmmm... I really should start thinking of some better alternate names for that literal walking pile of shit.
>Booklight Spopple? Maybe...
>She hasn't been all bad.
>She's given me a place to live and paid for everything I've asked from her.
>Well, at least she's paying her dues for my services.
>I've been trying to get used to going to school here in Ponyville, but it's been years since I was in Primary school last. 
>I feel like i'm surrounded by a bunch of kids.
>Well, I am surrounded by a bunch of kids.
>Purplefart still hasn't found a solution, and I'm growing impatient. 
>These female hormones are playing havoc on my head.
>I mean, I wasn't exactly straight before hand, but I was absolutely not attracted to ponies.
>Not anymore, apparently.
>Every two seconds, I found myself fantasizing in one way or another about getting railed by a colt or being eaten out by a filly.
>I tried my hardest to force those thoughts out of my head, but it was impossible. They kept coming back.
>And it was getting worse.
>Even when i wasn't thinking about it, I could feel myself getting warm and wet in between my legs.
>It was the most alien feeling I had ever felt and the thoughts that came along with it weren't that much less alien.
>I've had enough.
>I had to ask Twiggy Boggle what the hell was wrong with me.

"T-Twilight?"
>God, I even sounded like a little kid now.
>"Glass? What's wrong?"
"N-nothing, I..."
>"Glass, something's up. You didn't call me "Fleshlight Spankle" or some other ridiculous name this time, so something is definitely wrong."
>Darn. Maybe she wasn't as mentally vacant as I thought.
"Fine. You got me. Something is... Wrong with my body."
>"What is it?"
"I'm having these weird thoughts lately... Like, I... Want... I want to... Do naughty things with other ponies."
>She stared with open eyes for a few seconds before blushing and laughing nervously.
>"Eheheh, uh, I don't know why you need to come to me about that. Everypony has thoughts, they just usually keep it to themselves. Or their special somepony."
"Do you really think I'd be telling you if it was just that? I can't stop! I can't stop thinking about ponies doing... Things to me. Even when I'm not thinking about it, I still feel all... Worked up and stuff."
>"Oh. Oh, I see..."
"What is it?"
>"It never really even crossed my mind. Glass, you're going through estrous."
"Estrous? Like that thing horses have?"
>"Well, yes, plenty of females do. Horses, Ponies, Dogs, Cats, lot's of creatures, really. What, didn't Humans go through that as well?"
"No! Even so, I wasn't a girl before!"
>"Well, unfortunately, there's not much I can do for you. The only way to get rid of it is to mate with another pony, which is technically illegal for you to do, seeing as you're a minor, or for you to just wait it out."
"I don't want to wait it out! I want it to be over!"
>"Well, you can... Ahem, "Relieve" yourself in one way or another.
>She can't be talking about...
>"I do have a few toys around here that I never got to use during my last estrous. I guess you could have them."
"No. Out of the question."
>"Well, you could use your hooves, but you run the risk of getting an infection. There's a lot more dirt on your hooves than you realize."
"No, I mean I'm not masturbating. I'm a bucking dude, I don't use dildo's."
>"It's your choice, but the offer is there if you want it."
>I walked out of the room with my face scrunched up.
>I could do this without masturbating.
>I am not weak.
>I am Anon, a strong, male...
>Green...
>Mare..
>Wet...
>Pussy...
>Getting filled with a thick, studded dildo...
>Set to maximum vibration level...
>Ravaging my tight little hole...
>GAH!
>NO.
>NO NO NONONONONONO, GET OUT OF MY HEAD.
>I looked down between my legs only to see as a drop of something splatted onto the floor behind me.
>I froze.
>I couldn't take it anymore.
>I sprinted back to the room where Twilight was.
"GIVE ME THE TOYS NOW."
>She sat back a little, surprised by my outburst.
>"Okay, Glass, jeez. Give me a second."
>I rocked between legs as Twilight slooooowly stoooood uuuuup and sloooooowly waaaaaalked to the dooooooooooooooooooooooooor...
"HURRY THE BUCK UP!"
>"Gah, Glass! Calm down, I'm going already! Jeez!"
>After what seemed like forever, she finally opened up a closet door and pulled down a box marked "DO NOT OPEN. THAT MEANS YOU, SPIKE."
>She opened it up and levitated a blue horse shaped dong out of the box.
>"I think you should get used to it first, so have this one as a starter-"
"NOPE" 
>I snatched the box from her grasp and ran as fast as I could.

>When I got to my room, I slammed the door and threw the box onto my bed. 
>I searched through the box for something to sate my thirst for release.
>I quickly settled on a studded vibrator, similar to the one I had been fantasizing about not that long ago.
>I lay back on the bed and stared down between my legs. 
>Holy fuck, I was soaking. 
>It had never been this bad before! My legs were practically drenched in the sickly sweet, musky scented juices that had come from my virgin hole.
>I felt all strange and squirmy as I imagined it inside of me, my mouth opening and letting out a quiet moan.
>I hastily picked up the vibrator and began fumbling with it, looking for the controls. 
>I eventually found it, a small switch on the bottom with three settings.
>I didn't even read the settings and immediately set it as high as possible.
>I nervously placed it between my legs and shakily brought it to my lower lips.
>As soon as it came in contact with my parts, an all encompassing feeling of bliss took over me.
>I slowly slid the tool inside of me, rolling around as I let my entire body quiver with pleasure.
>I thought at first that this would be just like when I was a guy, concentrated at the crotch and not very pleasant until climax, but the opposite was true. 
>The entire experience was incredible. 
>I slid my legs around, feeling the buzz of the toy emanate throughout my entire body. 
>Granted, the pleasure was focused mostly on my crotch, but it spread like wildfire, with my pussy as the center.
>I wiggled it around a bit, stimulating all new parts of my relatively new hole, moaning in pleasure and closing my eyes.
>I imagined Scootaloo with her head between my legs, lapping away at my juices as they spilled down onto the sheets.
>I pulled the toy upwards a bit and felt a huge surge of pleasure as I hit something near the rim of my pussy.
>What was that?
>I opened my eyes and moved the vibrator around a bit more.
>Could it be my...
>I moved the vibrator upwards again and pressed it heavily against my clit.
>Instantaneously, I felt myself jolt in pleasure again.
>This!
>This was where it's at!
>I moaned even louder and pressed the tip of the toy into my clit, shuddering at the feeling it brought and causing a strange pressure to build up in my stomach.
>I held it there, panting as the pressure built and built until it felt like there was no where left to build and then...
>White.
>My eyes were filled with nothing but white as a huge shudder overtook my body and the pressure building up deep inside exploded out like a damn wall shattering.
>And it might as well have.
>My pussy squirted a clear fluid out a few inches, coating both the bed sheets and my legs.
>I let out a loud, high pitched groan as my brain was filled with an overwhelming pleasure. 
>There was no way... No way I could ever go back... This was too good...
>I had no idea if it was the heat of the moment at the time, but if this was how this felt... I never wanted to go back to being a man. 
>I felt the vibrator drop from my grasp and fall to the bed.
>It was at that point that I resolved myself rest.
>Any worries of Twilight walking in were erased from my mind as I let myself fall asleep, basking in the still remaining glow of my first orgasm as a filly.