Testing For Knowledge

by Nagiman

Rating: mature
Tags: My Little Pony: Friendship is Magic, Rainbow Dash, Porn, Sex, Fetish, Twilight Sparkle, Anthro
Length: 5109

Twilight invites Rainbow over to help with a science experiment, Not what Rainbow expects.

Rainbow has always had a dream to screw the pooch, quite literally. When Twilight invites her over to do some experiments, she finds out that she'll get to fulfill her dreams. However Twilight has some other things in mind for "testing".

Rainbow is willing to do anything to get her hands on that preview of Daring Do that Twilight is offering her, even if it's the worse sounding thing in all of Equestria.

Warning: This Story contains Shit, Urine, Sex with a Dog, 2 Futa Mares, Dirty Dirty Sex, and a little bit of Sounding.

You have been warned of what's included, only for those who are brave enough to face the 7 rings of hell and come back.

Published 2020-02-28 16:50:01 UTC
Last updated 2020-02-28 16:50:01 UTC

1 Dog, 2 Mares, 3 Cocks

Rainbow Dash had just landed at the door to Twilight Sparkle's castle in Ponyville. She had a note in hand that read "Rainbow, I'm in need of some help at the castle with some experiments, in exchange I have a preview of the newest Daring Do book. If you do come, let yourself in. Spike will be out, so just look around or give a shout. -Twilight". Rainbow gave a shrug opening the big oak door to the palace, closing it carefully behind her not to slam it hard. Rainbow looked down the hallways to see if there was an obvious sign where Twilight may be, but nothing stood out from the lobby. The cyan mare walked toward the chamber where the friendship table was, maybe the egghead was in there. Opening the center chamber revealed nothing to her, no signs of usage in a while and still no signs of Twi.

Walking back out into the main hall Rainbow yelled out, "Twilight, I'm here! Where are you?" Her voice echoed through the empty halls of the castle. From the distance a sound was faintly heard echoing back, but it didn't sound like a voice, it sounded like a bark. "Barking? I don't think Twilight owns a dog." Rainbow was confused at why there would be a dog in the castle. Following the sound, it lead the pegasus to the alicorn's personal chambers. It was clear as day that the sound was coming from behind the door along with the shuffling of heels clicking along the marble floor. Rainbow pushed the door open to see the commotion going on inside.

On the inside was Twilight Sparkle, she was dressed in a white lab coat, black short skirt, black t-shirt, heels, and her horn rimmed glasses. She had a dog running around her legs while she was trying to set up a camera. It was black and light brown from head to tail, and deep brown eyes. Rainbow determined it to be a german shepherd that Fluttershy talked about so much. The dog had noticed the new pony in the room and took of running to her. Jumping up and down trying to get to her face, Rainbow crouched down to welcome the furry friend with some petting as the dog went to town licking her face.

"Thank goodness you're here Rainbow, I wasn't sure you were coming or if I'd have to conduct the tests alone. It's much better to have an outside participant than just myself, that way I can document everything easier without much interference." Twilight was clearly worked to death from the dog's energy. "As for the canine, I borrowed him from Fluttershy for the tests for my theories. His name is Swiff and he's got a lot of energy to work off."

"I can see that but how do I come in to this whole idea. Just being the fill in for you so you can take the notes?" Rainbow gave a questioning look towards the lavender mare. "Cause if that's it, I don't mind, especially if I get that sneak peek of Daring Do afterwards."

"Well to answer your question, yes you would be my fill in. I couldn't think of another pony who as big of a cock as me that would be willing to help without wanting a whole lot more. I do have to warn you though, it will get messy during the experiments so I hope you can stomach some things."

"Wait what? You want me to screw the pooch. Are you trying to have Fluttershy kill us, my cock will split this guy in half if I tried to." Rainbow's tone voiced concern greatly for Swiff and for her own life if the yellow pegasus found out she was the one to hurt him. Deep down, Rainbow really wanted to fuck some of Flutter's animals. Every time she was there she would stare at the different dicks and vaginas of various exotic nature. This was her chance to get some action, even if it meant doing it in front of her friend.

"No no, well yes. I want you to fuck him, but not with your dick. I want him to fuck you his penis. My goal is to find out how stimulating different penis's are for mares. As for you, I want to be able to add extra stimulation if needed using my magic." Twilight was blunt with her words. However she was planning on much more than just a simple sex thing.

Rainbow pondered for a bit, leading the purple alicorn on that she wasn't so sure. She didn't want to give away that she wanted to do this at all, but then Twi's words rang through her head again. "Messy, what do you mean messy that I can stomach it. Don't you remember when I drank most of that spoiled cider barrel?"

There was a time when Rainbow and the girls were over at the apple farm drinking with Applejack, and the blue pegasus cracked into a new barrel and drank it nearly bone dry before AJ noticed the seal was broken on it. That meant it wouldn't cure the way it was supposed to and instead it spoiled. Opening the front of the barrel brown sludge spilled out onto the floor and it smelled horrid. Rainbow didn't feel anything wrong with her stomach, not until the next day. She had regretted chugging down that barrel.

"Yes, I remember. The next day you called crying like no tomorrow that you hated your life. As for messy, if you are willing. I want to test his urine and feces with you as well. You can walk away if you want to, I won't blame you, but if you go through it, my ass is yours for the next week at any time you need a fuck." Twilight was trying to cover her embarrassment and a bit of shame of what she just asked her friend to do.

"So let me sort this all out. You, Twilight, want me to let this dog fuck me, and you want him to piss and shit on or in me during our sex while you film and record results. Do I have this correct?"

"Exactly what I want. So are you willing to do it? I have the preview right here." Twilight levitated the about thirty pages of unbound script in front of the cyan mare, proving she wasn't lying when it came to her end of the offer.

"As long as you don't mind lying to any medics if I have to go to the hospital. I also will make full use of your little tailhole too when it comes to next week as well. So when will we be starting?" Rainbow made clear with the gesture with her fingers one being straight out, the other hand forming a hole, and making movements of in and out.

"We can get started once I finish getting this camera ready. Could you distract Swiff away from here for a couple minutes while I finish up. You'll also be using my bed there so you won't be laying on the stiff floor. I've already cast a spell on it that makes it so stuff won't seep into the blankets or mattress so go ahead and make as big of a mess as you want."

Twilight took to setting up the camera as fast as she could making sure to get the angle right, along with the lighting of the room. She wanted perfection for her notes and for the perfect example footage in case she missed anything and had to re-watch later. Dash had gotten Swiff over to the bed and up on it, giving him all the petting and belly rubs he could handle. His tail was a furious storm of happiness, that it could easily be mistaken for a weapon at the speed it was going. Rainbow in exchange got faces full of slobbery canine kisses, her face attacked by an onslaught of thankfulness. After a few more minutes the purple pony finished getting the camera set, and pulled over her clipboard, chair, and side table with quill and ink pots sitting on it.

"Alright Dash, I'm set to record and take notes. Fluttershy gave me signal words for Swiff so I can control his actions with ease in the bed. Swiff, snuggies. Rainbow get yourself ready." Twilight pressed the record button on the camera, letting the blue pegasus know that it was time to strip.

Swiff rolled over on the bed, exposing himself to the camera. His balls hung over his anus, and his sheath now letting out his red rocket. Slowly expanding out and growing, it was a spectacle for Dash to see it this close up. She gave her lips a lick, as it hit full size. Looking like a full tube of lipstick in a ruby red shade with a small bulge near the bottom for a wider girth than the rest of it. Rainbow started to strip, removing her t-shirt and throwing it aside leaving her pink bra on. Her breasts weren't amazingly huge like Pinkie pie's were, but they were certainly bigger than Applejack's flat chest. Next she dropped her shorts and kicked off her shoes. This left her standing with some plain looking white and pink striped panties.

Dash turned to the camera and blew a kiss with a wink to it. "Like what you see Twi? Cause that's just the start." Dash then unhooked her bra from the front, teasing the purple mare by covering her breasts with one arm as the restraining fabric hit to the floor. Shuffling her arms back and forth and twirling around to taunt the alicorn watching waiting to see it all come off for her project. Finally Dash had stopped and showed off her tiny sweater puppies to the camera. Time came to drop her undies, with both hands she slipped them into the sides, and made one swift motion to drop them down. Standing to attention Rainbow's fuck stick was hidden in it's own sheath, her balls swinging in the air like apples hanging on tree branches.

"Come on Dash, enough teasing, start having fun with Swiff. He clearly needs some help since he doesn't have hands like us." Twilight pointed to the dog on the bed. Down below her skirt however she felt her own dick poking out of her sheath and poking into her panties. Trying her best to ignore the snake in her drawers she focused on taking down notes.

"Well what do you need to me to do while I fuck this cutie?" Rainbow asked, staring at the sweet treat waiting for her. Her own member slowly started to peek out of it's hiding hole.

"Let me know, how it feels, tastes, anything you may be experiencing. So why not start with just feeling his penis, and do some stuff and let me know the details." Twilight put on a smile as she dipped her quill in an ink pot, and set it to the paper ready to write everything she could.

Dash turned toward her furry companion, and climbed up onto the bed with him. Laying down between his lower paws to get the best view and easiest access. Rainbow leaned in and gave a whiff of the dog groin. It smelt like a gym towel that was sitting in the bag for a week since the last use. Taking hold of the genitalia in one hand, she caressed it gently, letting it rest in the palm as she moved her hand along to get a feeling of it.

"It's smells Twi, not really bad, but not great either. As for how it feels. It's veiny and soft, with a small amount of smoothness to it. Definitely different than mine or yours." Rainbow was still giving a light hand job to Swiff as she was describing it all out.

Twilight wrote down on her clip board, still staring at the scene before her. Rainbow was now giving the red rocket a good licking, going up and down the shaft. Eventually she gave his balls a try, but couldn't keep them in for more than a few seconds before spitting them out. The hair covered nuts weren't very good, she much preferred a smooth clean pair in her mouth. Taking back to the cock, Dash went and started with sucking onto the member. Swiff let out a little whimper of joy, and annoyance at the teasing. His tail was still wagging, it was tickling the blue pegasus's chest with it's fluff.

"Dash roll over onto your back, I've got a way to make your work a bit easier." Twilight rolled her finger gesturing for the flip. Dash gave an odd look but let go of her treat and flipped over. "Good. Swiffy, fun snuggies." The dog's ear's perked up hearing his queue for some change.

"What's going on Twi, I thought you needed me to tell you everything?" Rainbow had a questioning gaze on her face as the dog got on all fours making its way towards Dash.

"Don't worry, I've got a recording remember. You can tell me later with your mouth being occupied so much." Twilight just gave a smirk as if nothing was wrong. Down lower though her cock was reaching critical erection status, as it was throbbing beneath the cotton restraints.

Rainbow was about to say something about the purple ponies bulge when Swiff jammed his cock into her open mouth. This was a big surprise for her. The dog had taken control of the situation, and she was now the toy. Swiff humped rapidly into the blue mare's pie hole. His little member still big enough to poke into the back of her throat. Dash was now fully aroused, her fuck stick fully erect and throbbing. As her mouth was being filled with red rocket, she started to stroke herself to add into the pleasure. It was a dream come true for Dash, and for her friend to watch her indulge was even better.

"Swiffy, wee wee sweetie." Twilight commanded. She was now stroking her own cock as she watched the show in front of her. She had let it free from it's prison once Dash's face was seeing a lot of hairy balls.

With that one command the dog had stopped his humping, but his pecker was still deep in the mare's mouth. He then let out a stream of piss into the comforting hole. Rainbow went into a minor shock at the taste assaulting her taste buds. It was salty and bitter. It splashed around her mouth and flowed a little down her throat. Not wanting to displease Twi, Dash started to drink down her salty beverage. It wasn't as bad as the spoiled cider she had a few months ago. Guzzling down all she could, Swiff kept going hard. It seemed like he hadn't gone all day, most likely from being left in the cottage at long times and Fluttershy not wanting to come home to find a mess. Eventually the dog's stream had let up, til nothing but a few drips fell onto the roof of Dash's mouth.

"Good boy Swiff. Now doodies." Twilight had now taken to stripping her clothes off. Keeping on only her glasses and high heels. Her erection was going mad with it bobbing up and down without the need of touch.

Walking over to the bed, Twi climbed up behind the canine. Rainbow had a look of confusion on her face as her friend was now with them on the bed. Twilight then pushed on the dog's butt, forcing his member all the way into her friend's maw, and the balls now covering her nostrils.

"Swiff, doodies boy. It's okay." Twilight patted the dog's ass to reassure him it was fine to do his business.

Swiff lifted his tail high into the air, already in a squat. Dash was gagging on the cock in her mouth but then got the full sight of what was going to happen. The dog's puckered anus opened wide, the head of a small turd started to appear out of it. With that sight the mare closed her eyes, not wanting to get shit in them. Then came the first splat as the wet nugget hit her forehead. Twilight picked up the nugget in her head and gave it a lick. The taste being foul, like it was a moldy piece of toast. After the minor taste test, Twilight popped the whole nugget into her mouth, chewing on it. Mashing the bits of dirty fudge into her teeth and gums. Twilight was happy that she was getting part of her wishes fulfilled.

Dash on the other hand was now stroking her cock even faster as she was choking on the dog's dick. The feeling of being used as a toilet by the canine was better than expected. Swiff had quickly managed to drop five more long logs across her forehead and eyes. The warm feeling of the shit was good, even though the smell was strong that close to her nose. Once Swiff had finished his business he went back to a full stand. He then resumed his humping madly into the pegasus below him.

Twilight scooped off the brown delights from Rainbow's face allowing her to see again. Twilight took one of the long logs, and stroked it along her massive fuck stick, coating it in the feces. She made sure every inch was covered in the butt fudge. With the little that was left she reached under Swiff and grabbed his red rocket as he humped. This coated his cock at the same time as feeding it into Dash's maw. Swiff made a joyous bark, as he started to knot. His dick now jammed in the blue mare's mouth. The knot now big enough to be stuck in there good and too big for Dash to open wide enough to get it out. The taste of shit was on her tongue when a blast of dog sperm splattered inside as well. It was sweeter tasting than the piss, and less foul than the shit.

Dash drank as much as she could of the dog semen, but couldn't managed to keep up. It flowed out around her lips, leaking towards her eyes, and starting to fill her nose with more. Twilight seeing the leakage leaned down and licked up the white treat on her friends face. Swiff finished with one last little squirt, then proceeded to try and remove his dick from the mare's mouth. It wasn't budging and the tugging was annoying him. Dash on the other hand was scared that the meat stick wouldn't get removed.

Twilight remained calm and soothed both them. "Don't worry Dash, it'll just be a few minutes before his knot dies down. As for you Swiff, you did good boy. It's alright, just let the time pass." Twilight rubbed the dog's head to relax him. "Scooch over a bit Dash, so I can reach your cock. Might as well keep you happy while he shrinks down."

Dash with her mouth full of canine swiveled her lower half towards her purple friend. When enough had gotten closer Twi grabbed another one of the brown logs and started on a hand job for the blue mare. The warm sensation that was cooling on the air as it smudged along the blue shaft was a nice feeling for Dash. It was interesting indeed. Never had she expected to do that, let alone somepony else do it to her. After a few minutes of stroking, Swiff's knot had shrunk freeing Dash's mouth from it's open position.

"Oh thank Celestia. I thought I'd never talk again. Twilight, I don't know what's gotten into you, but I'm liking it." Dash worked her jaw up and down getting the blood flowing again.

"Well I think you'll enjoy this then." Twilight climbed on top of the awaiting pal. Getting into position, Twilight angled herself so that she could suck on her friends now muck covered dick, and she could get hers sucked as well.

Twilight was first to start digging into the sixty nine position, devouring the blue pecker in a quick dive. Rainbow moaned her pleasure to the heavens. As the purple mare went deeper, swirling her tongue along every vein, across the tip, and along the underside, Dash couldn't help but wrap her legs around Twi's head. Locking the new fuck toy around the dirty fuck stick, Dash took to returning the favor. The taste was bearable around the meaty meal she was enjoying. It still had a foul taste, but not as strong as the smell from the other shit pieces near her face.

While this happened, Swiff had moved over to the side, cleaning himself and watching the show evolve in front of his eyes. For the mutt it was quite a show seeing two ponies going hog wild on each other. Enough so that he started to get hard again. He got up and moved over to the two mares and started to lick the purple pucker at his head level. Twilight reacted with a quick glance back thinking Dash had done it, but her mouth was still full with the fudge covered hose. An idea was brewing in the mare's head.

Twilight let go of her tasty treat, saliva stretching from her jaw down to the tip. "Dash, let's switch up things. Come round front of me, Swiff is ready for another round and I want to give him a try."

Dash perked up to the voice in the pleasured love. "Ah.. okay then." Letting go of her leg grip, she rolled out from Twi, and moved to her front. Staying on her knees so she had easy access to her new fuck hole. "If we're switching up then put this in your mouth." Dash held another of the shit logs in her hand up to the mouth of the purple pony princess. Twi opened wide and was fed the terrible treat. "Now let's have fun."

The blue fuck stick was jammed into the maw, mashing the turd into it. Twilight knew exactly that her friend wanted to go with this. Not swallowing what was in her mouth she started to use her tongue to break it up so it could coat and swirl around the intruder in her mouth. Swiff was whining as his red rocket hardened from watching the two ponies. Twi held her cheeks apart for the poor dog, who then took the invitation. Climbing on top of the purple pony, the dog humped around trying to find the hole for his meat to go into. After a few attempts he found a hole, but not the one Twi wanted him in. He landed his rocket into her fudge factory. It pushed in on the dry unlubricated anus, spreading it wide.

Swiff let out a joyous bark that he was now getting his pleasure. The purple mare had tears streaming from the pain in her ass, literally. Swiff did a few short pumps trying to make sure he didn't slip out. After a few of those he started into his frantic fucking, pounding his doggy heart into his new bitch. Twi was starting to adjust to the pain, as she gagged on the blue dick in her mouth. The saliva was mixing with the shit to make a brown goo that dripped out of her maw, down her chin, and pooling onto the bed. Dash was loving the new experience altogether. Grabbing onto the back of the mare's head, she started to pound the throat of her fuck toy harder. This pushed shit down Twi's throat straight to her stomach.

Twilight was in heaven at this rate. Even if her plan wasn't fully going as thought out, it was still enjoyable. Shit in her belly, fucking with her friend, and getting to try some new style of cock. In her pleasure Twilight started to stroke her own meat, as her fuck mates went to town on her.

The first one to come was Swiff, his rapid thrusts were a good indicator of him being close. His knot growing to a large size stretching the poor mare's ass to a crazy size was the seal of the deal. Warm gooey dog jizz poured into her ass, coating the aching walls with soothing love. Swiff let out a howl signaling he had claimed his bitch, as he continued to thrust with the jammed knot. Twilight moaned against the dick in her mouth, causing vibrations to pleasure her lover.

Next to blow was Rainbow. She shot her load right down the throat of the princess, coating it with white tasty baby batter. The mix of shit saliva added a slight enhanced taste. When Rainbow had finished with the main blast, she pulled her cock back a bit so Twilight could swallow the now mashed up foul fudge. With a sigh, Dash squirted one last time coating the last of Twi's meal with her cum.

"Go ahead, swallow that, cause I need to pee too and I'd rather not get out of bed at this rate." Dash tapped her nose at the mare staring at her.

The purple princess got the hint, she quickly swallowed the meal ready to accept a good helping of refreshing piss. Rainbow let out a sigh as she let go, spraying the yellow liquid all over the insides of her cock comforter. Twilight drank down her salty beverage with glee, to the point of having it all and still sucking hard on the cock so it would go faster. The pegasus stroked her friends mane as if she was a dog as well. She truly was a useful kinky bitch, but she could've asked for this kind of treatment. After the urine ran to a trickle, Twi lapped up the last few drops from the tip and let the dick fall from her mouth.

With a cough Twilight recovered her composure. "I'm so glad to have joined in the experiment, but I'm not finished yet." Twisting onto her back, Twilight grabbed the last piece of shit, holding it still, she lined it up with her urethra. With a quick spark of magic it expanded the fluid chute enough so she could hold it open. Shoving the crap into her fuck stick it caused her slight pain at the new intruder. Not wanting to go without a bang to her orgasm, she endured through. Swiff was now at a better angle as his knot was waiting to shrink down. Just waiting for it all to be over, he was tired and ready for some rest.

Dash watched in some horror, a little disgust, and a lot of curiosity as the purple mare sounded her pecker with a dog's shit. Twilight now adjusted to the stinging started to stroke her member once again. Now smashing shit inside her pee hole. It was glorious of a feeling that she wished she had done before. As she went to town on herself there was a rumbling in her stomach. The mare had to take a shit, but she was currently blocked off, but that wasn't going to stop her.

Twilight grunted, as she tried to push the pile out past the current knotted blockade. It was hard and painful as she grunted louder and louder. Dash was wondering what she was trying to do then realized what was happening. She acted quickly, pushing at the now tired hound trying to get him to pull his red rocket out. Twilight kept up her assault against the blockage in her ass. Her shit was now starting to make some head way but it was painful having the knot being pulled out at near full size. This pain was what sent her over edge. Twilight blew her load, not only spraying jizz all over her face, but sending bits of shit as well. Painting a nice brownish white mix along her breasts, glasses, and neck.

With all the pressure against the cock, it popped out finally freeing the shit from it's narrow prison. However the pressure that was exerted on it caused it to become a brown sludge that leaked out onto the sheets, pooling around the purple ponies booty. It was a euphoric finish to a wonderful session.

"That... that was... amazing Dash. I can't feel my legs after all that. We'll have to do more testing another time." Twilight was panting hard, lungs taking in all the air they could. "You've held up your end of the deal, now I'll hold up mine. Over on the chair is the preview, have at it."

Dash got off the bed, walking over to the chair. Picking up the paper bound with a clip she started to read. However the writing wasn't from Yearling, it looked like hers, in fact it was hers. It was pages from her diary stating her deepest desires for sexual pleasures with an animal. Her face went from shock to embarrassment to anger. She didn't know what to feel, her friend took pages from her diary, read them, then used her for some sex experiment.

"I know what you're thinking Dash, and yes I am sorry, but at the same time I know you are happy down inside getting to have lived out your dream of some animal fuckery." Twilight had a teasing grin slapped across her painted face.

"Twilight, I could kill you for doing this, but at the same time I won't cause you did me at least one good thing. However, I'm not gonna let you off the hook that easy. Just watch your back for a while, cause I'll get you back with something worse." Dash picked up her things and marched out of the room in a huff.

Twilight rolled back over, cuddling up next to Swiff. "I wonder if she remembers that I filmed all of that. Oh well, at least I know I have something to fight back with, let alone some fun watching material." Twilight hovered her clipboard over to the bed side. On the paper was a sketch she worked on of a very detailed image of Dash exposing herself fully without her cock. Twilight then made the quill come over, she added the detail of jizz, shit, and urine. With a flash of light the paper vanished from her hands, where she had sent it, only she would know.