The Horse Experiment

© by flosiedon

Matt looks around groggily at his surroundings, thinking about what happened. It appears that he was in a stable and was naked on his hands in knees with his dick hanging down from him. He looks to his right and sees his twin sister Ally in the same position. This was the first time he had seen her naked in a while, and she was hot with her DD cup tits hanging down. The room is dark, with many empty stables around.

Then, the doors to the stable open, and sunlight floods the room, making Matt squint his eyes to see what is happening. The doors close quickly, and he sees a man walking into the room with a big bag. He walks over to his twin sister, puts the bag on the bench, and starts talking to them.

“I bet you are wondering why you are here,” he says.

His sister and he don’t respond.

“You are here because we are experimenting, and you were chosen for certain qualities…”

“But we’re only 19,” Matt pleads.

The man continues, “This experiment will hurt. I will tell you that, but we will have created something miraculous when it is over.”

He walks over to Matt and says, “We will start with you.”

Then he opens his bag and takes out some lube and an assortment of dildos. He puts on a glove and sticks his fingers into the lube.

Matt can see what he is doing and begin to protest, but his voice is cut short when he forcefully sticks two of his fingers into his ass. The feeling is weird. It is painful and pleasurable at the same time. It is all over quickly, though, as he retracts his two fingers covered in lube and walks over and takes a 6-inch dildo and walks over and places the tip on Matt’s ass.

“If you are going to handle what happens next, we are going to need to loosen you up first,” the man says.

He pushes the dildo slowly into his ass before finally bottoming out. The same feeling comes over him as Matt can feel the dildo inside of him. He then takes it back a few inches and starts to thrust it back and forth, creating a rhythm. Matt grunts from exertion as he is doing this. Then something really weird happens, and he starts to get a boner. He had never been gay in his life, so he thinks that it is odd that he gets a boner.

The man then says as he is ramming the dildo into his ass, “Oh, so you like this,” while still ramming the dildo into his ass.

He then goes back to his bag, takes out an 8-inch dildo, and does the same thing. The 8-inch dildo makes Matt feel fuller than the 6-inch dildo. As he is ramming the dildo in, he can start to feel his ass getting looser and looser. After about five minutes of the man ramming the dildo in his ass, the man says to him, “You are almost ready. One more thing I have to do to get you ready for the main event: clean you from the inside out. ”

He then goes over to his bag and removes a tube attached to a big water bag. He goes over to a hose on the wall and fills the water bag. The bag must have been big enough to hold a gallon. Then he takes the bag and hangs it on a hook above him that Matt had not noticed before. Matt thinks he recognizes the bag from some of the porn he watched. It was an enema, he thought. He then takes the tube and proceeds to stick it right into his already loosened ass.

“I am going to need you to be clean in there if my experiment is going to work,” the man says.

He then turns a valve, and the water starts to flow into his ass. Matt can feel the cold water flow into his ass, making it expand. After a minute, he can feel his belly expand, and he looks back and looks like he is pregnant. Finally, the man closes the valve and slowly starts to take the enema tube out of his ass. As soon as he does this, some brown fluid shoots out of his ass and onto the floor. It feels really weird having the liquid shoot out of Matt’s ass. He then proceeds to put the enema tube back in.

Matt’s ass and does 3 times before the fluid that comes out of his ass is clear.

The man pulls out a walkie-talkie and says, “He is ready. Bring him in.”

Matt turns around and sees the doors to the barn open, and a man walks in, directing a stallion behind him. ‘Oh no,’ Matt thinks, ‘this can’t be.’

The man then walks over to the stallion and starts to rub it cock. Before long, a 2-foot-long cock springs out from the horse.

Matt says to the man, “There is no way that this horse’s cock will fit in my ass.”

“Well, it has to,” the man says.

The man then presses a button on his remote, and the straps holding his hands and legs to the ground tighten. He is lifted into the air on a platform he was on that he had not noticed before. The platform stops at the perfect height for the horse to penetrate his ass. The stallion then rears up and places both hooves on a bar so they will not be on Matt. Then the stallion starts to thrust, searching for his hole. Matt starts to prepare himself for the inevitable.

Finally, after four or five missed thrusts, the horse finds his hole. At first, the horse can only fit the apple-sized tip of his dick into his ass. The horse then begins to thrust his dick further and further into his ass. Finally, after a couple of minutes of the horse going deeper and deeper into his ass, the horse bottoms out and stands still for a couple of seconds.

The pain is excruciating. Matt almost blacks out from having the horse dick so far up his ass. Then, the horse pulls out six inches and thrusts. He repeats this action and then forms a constant rhythm. The pain begins to subside, and the pleasure kicks in. Before long, he can feel his dick start to shoot off on the floor. Then after ten minutes of straight fucking from the horse, he can feel the horse’s balls tense up.

The horse then bottoms out, and his dick erupts with cum. The hot fluid feels so good inside his virgin ass. The ropes of cum cover the inside of his ass and begin to make his ass expand. The horse keeps cumming for about a minute. Finally, the horse stops, and right as the horse pulls its dick out of him, the man puts a but plug in.

“Now we don’t need to waste any of that cum do we,” the man says.

He then lowers the platform, takes the straps off Matt’s legs and hands, and collapses on the ground. He feels so bloated, and he looks at his stomach, and it looks like he is pregnant from all the cum inside of him. He can feel it swishing around in his ass, and it feels kind of good. Then he passes out on the floor.

****

Matt wakes up on the cold ground naked and looks at himself. His stomach bulges with all the cum inside of him, and his ass ached, and Matt tries to stand up but cannot. He looked around and saw that he was in a horse stable. He then turns and looks at his twin sister lying next to him naked. She, too, had a stomach that bulged like she was pregnant, but she still looked sexy. Matt could see her B-cup tits because she was lying on her back and her beautiful pussy with just a little tuft of hair at the top of her slit. His cock started to grow, but at that same moment, she woke up.

“What happened?” proclaims Ally.

“I don’t know, says Matt, “we were going to summer camp and then…”

Matt looks over at Ally and says, “Did the horse…”

“Fuck my pussy?” says Ally. “Yeah, it did.”

Matt then hears the doors to the barn open and eyes the man as he walks into their stable.

“Rise and shine, boys and girls,” the man says, “I bet you have been wondering what the experiment I performed on you was for. I didn’t want to tell you yesterday to spoil the surprise, but here we go. Those two horses you had a little fun with yesterday were normal. I genetically modified you and your sister to get impregnated by any creature.

“I also modified the time the pregnancy will take to make it go from 9 months to one month so that you will feel changes pretty soon. Another thing is that the reason I plugged up your holes from letting the cum seep out was because the creature’s cum takes about 4 hours to impregnate you. I wanted to do this to create the greatest horse ever. I could not do this by mating two horses together, but I had to mate a horse with a human because, with a human, the horse can be very intelligent.

“I picked you two because you both have high IQs, are athletic, and it looked like you could handle this. And I thought it would be fun to have a brother and sister. Oh, and by the way, my name is Dr. Jekyll. Any questions?”

Matt says, “You cannot be serious. There is no way that I can be…pregnant.”

“Oh, I am quite serious,” Dr. Jekyll says. I have given you, ah, I don’t want to get into specifics. Do you have any more questions?”

“Yeah,” Ally says, “How will the foal come out of our…”

“Well, your bodies will be changing to accommodate the foals, but it will still hurt very much,” Dr. Jekyll says. “It will probably hurt more than a normal pregnancy, so be prepared. You will stay here in this stable for the remainder of this pregnancy. Oh, and one more thing.” Dr. Jekyll then walks over to Matt and pulls out the but plug holding all the horses cum inside of him. The cum shoots out of his ass and all over the concrete floor of the stable. He then pulls the plug out of Ally and says, “Well, I hope that this semen did its thing.”

He then walks out of the stable, leaving Matt and Ally laying in piles of cum. They both sighed out of relief when the cum was finally out of their pussies and asses.

“What are we going to do now,” exclaims Ally.

“I don’t know,” says Matt.

Matt then lays on the ground in his pool of cum, thinking about the events that happened yesterday. Then the man walks into the stable and says, “Here’s dinner.”

Then he walks out of the room. Matt crawls over, gets the two buckets, and brings them to Ally.

Ally gives Matt a puzzled look, and he just shrugs it off. He then takes a handful of the grain and eats it. “It’s not that bad,” says Matt.

“Yeah, right,” says Ally

She then tries the grain and agrees with Matt. They could have probably eaten anything at the moment. They had not eaten anything in a while and were both very hungry. They then took turns sipping water from the bucket until it was drained. They then fall asleep on the cold concrete.

****

Matt wakes up first the next morning and feels different. He feels a weight on his chest and looks down and sees that he has some A-Cup tits. His hips had widened, too, and his stomach was a little bloated. His ass also did not feel sore anymore. He looks over and sees his sister awake as well. He could see that she also had changes. Her hips had widened, and her tits went from an A to a B-cup. He then hears a giggle come from his sister.

“What’s so funny,” Matt says to Ally.

“Nothing,” Ally says, “That was quite the experience we had yesterday.”

“Yeah,” Matt says, “It hurt at first, but after a while, it felt really good.”

“Yeah,” Ally says, “The horse’s big dick felt so good in my pussy. The best part was when he cum. It was so great that it gave me the best orgasm I had ever had.”

“Are those real?” Ally says, pointing to her brother’s tits.

“Yeah, unfortunately, they are. I think that this is one of the side effects.” Matt says, “Feel them if you do not believe me.”

She then walks over to Matt and places her hands on his tits. Matt was shaking in anticipation of this and lets out a small moan as she placed her hands on his tits and started to feel around. Ally then said to him, “You can feel my tits if you want.”

Matt then places his hands on his sister’s B-Cup tits. Ally, too, lets out a small moan as he does this. Ally’s tits felt so good in his hands. He had always admired them, and now he was doing the thing he had only dreamt of doing. Her tits were the perfect size, and they were still firm. Matt then wanted to take it a little further. He took one hand off her tit and started to move it down her body. He reaches her clit and starts to rub it.

Her body shook violently as the orgasm went through her whole body. After the orgasm was over, she said to her brother, “Now your turn.”

She then grabbed his already hard cock and put it into her mouth. She started to suck his cock and massaging his balls at the same time. Matt could feel his sister sucking on his cock, licking the tip every once in a while. Then he could feel his balls tense up, and he said to Ally, I am going to cum.” Matt could then feel Ally start to deep-throat his cock. Matt then erupted with cum and then shot it all down his sister’s throat.

Matt then took his cock out of his sister’s throat and picked her up, and laid her in a corner on the hay. He then took his 8-inch cock and directed it into her awaiting pussy. He pushed in slowly, not wanting to hurt his sister. Finally, after a little pushing, he could feel his balls rub up against her ass.

“Are you ready,” asks Matt.

“Give it to me,” replies Ally.

Matt then pulls out and slams into his sister. He then started a rhythm, and he could feel the precum dripping out. His cock feels so good, with his sister’s pussy enveloping it. After what seems like an eternity, Matt can feel his balls tense up, and he goes hilt deep and cums into his sister as hard as he can.

They both lay there for a few moments with Matt’s dick still in his sister’s pussy, and that’s when they heard someone clapping. Dr. Jekyll had been watching the whole thing and was astonished. He had never thought that this would happen.

He then said, “Bravo, you two. That was quite the show.”

Matt and Ally blushed as they thought about what had just happened. What made it even worse was that someone had seen them do it. Matt then pulled his semi-hard dick out of his sister’s pussy, and a little stream of cum followed after that.

After a few awkward seconds, Dr. Jekyll says, “Well, the reason I came here was because I needed to feed your kids,” pointing towards their bulging stomachs, “The best way to do that is by the semen from their fathers.”

He then leads them out of a stall and into another stall where both their horses are kept. The black one was Ally’s, and the brown one was Matt’s.

“Well, I will leave you two to get to it,” Dr. Jekyll says as he backs out of the room.

They stand there for a few minutes when Ally says, “Well, I will go first to show you how it is done.”

Matt watches as his sister takes the huge horse cock and sticks it in her mouth, and starts to suck on it. Matt then watched as she took her hands and started to jack off the horse’s massive dick. Soon, he could see the horse’s balls tense up and knew what would happen. He could see her struggling to swallow the massive amounts of cum from the horse. Still, soon he could see that she couldn’t take it anymore, so she pulled the horse’s cock out of his mouth as it was still cumming, and it cum all over her petite body. This turned Matt on very much, and soon he had a big boner watching the horse cum all over his sister.

Soon, the horse was done, and Amy turned toward her brother and said, “Now it’s your turn,”

Matt had not been thinking about what was about to happen. He walks over to his brown horse and starts to rub its cock. Soon the cock is at full length, and Matt just stares at it.

“I don’t think I can do this,” he says to Ally.

“Yes, you can. Just do what I did,” Ally says encouragingly.

Matt then takes the whole cock and puts it into his mouth. He starts to suck on it, at the same time jacking off the horse with his hands. Matt loves sucking the horse’s cock. He can taste the precum oozing from the horse’s slit, and he loves it. Soon the horse’s balls tense up and send ropes of cum down Matt’s throat. Before long, Matt’s stomach is full, and he pulls out the cock from his mouth. The horse’s dick then starts to shoot cum all over Matt’s body, covering him from head to toe.

Dr. Jekyll walks into the room and tells the twins, “Oh, you two are a mess. Go back to your stable.” Matt and Ally comply and follow them back to their stability. He then puts a bucket of cold water and a horse brush and says to them, “You two should probably clean up.”

They then grab the bucket and scrub each other, focusing mostly on the ‘sensitive’ areas. This routine goes on every day for a couple of weeks. They wake up, have sex, get covered in cum, and then wash each other. Their bodies go through many more changes as well. Both of their hips get wide enough to accommodate the horse. Their tits swell up in size too. They go all the way to the D-Cup and stop. Their stomachs keep expanding rapidly in size, too. With about a week left, it looks like they are both having quadruplets in their stomachs. They have to stop having sex because their bellies are so big, but they can still feel each other up.

****

Then, one day, Dr. Jekyll enters the room with a box of dildos. He says to the twins, “Here, these are for Matt. If you want to deliver this horse without any damage then you will need to work on making your rectum big enough to accommodate this horse.”

“What about me?” says Ally.

“You should be fine, women are meant to give birth, and I think that your vagina will do just fine.”

The man leaves, and Matt goes over and looks at the dildos. They are not that long, but some of their girths were huge.

“Want to help,” Matt said to Ally.

“Sure,” Ally says, “Now get into the position.”

Matt gets on his hands and knees, and Ally chooses the smallest dildo and penetrates Matt’s ass slowly. Matt moans because he had been craving having the horse dick in his ass for a while, but he knew that it would hurt the foal. She then worked her way up to the biggest dildo, which was as wide as the horses dick. She did this every day until one day, Matt had some sharp pains in his stomach, and soon after, his sister did too.

They both knew that their foals were coming and started preparing themselves. Out of instinct, they both lay on their sides because that is how horses normally give birth. They both yelled as they went through the first contraction.

Dr. Jekyll came running in, said, “The show has just begun,” and brought a chair to watch the festivities.

They went through contraction after contraction together until twelve hours in, Matt felt he needed to push. He started to push and could feel the horse sliding down his colon. He pushed until he looked back and could see the head out.

‘Almost there,’ Matt thought.

The pain was excruciating. He kept pushing and pushing until the front legs popped out, then the back legs popped out after and he was done. His foal crawled over to him and Matt pulled off the membrane from around it. The horse then started to suck on Matt’s tit. The feeling was amazing as he could feel the milk leaving his body and into his horse.

“Nice job, Matt,” Dr. Jekyll says. “That is a beauty.”

Matt looks at Amy and sees her struggling to get the foal out of her.

“You are doing well,” Matt says encouragingly, “Almost there.”

Matt can see the head start to come out of his sister’s pussy. Ally keeps pushing, and soon the front legs pop out, and finally the back legs. Ally sighs as her foal finally comes out. The two twins then fall asleep with their babies sucking on their tits.

****

They wake up the next day and they both feel different. Their bodies had gone back to normal. Matt no longer had tits and widened hips, and Ally’s tits and hips had gone down in size as well. They were perplexed. Then, they could hear the barn doors open, and Dr. Jekyll walked into their stall.

“Hello,” Dr. Jekyll tells the twins, “You two did a nice job yesterday.”

He looked at their perplexed faces and said, “There was one more thing I did not tell you about when I modified your bodies. After you give birth, the changes that were made revert, and you look just like you did a month ago—unless you want to keep the changes.”

“No, no,” says the twins in unison.

“OK, I bet you have been wondering what your parents will think when you return after being gone for a month. Well, when I kidnapped you, your parents were going to send you to camp for a month, and I have been sending them letters about all the fun you have been having. Do not tell anyone about what happened today unless you want me to release a video documenting what happened. From you having sex with each other, with a horse, and giving birth. Are we clear?”

They both nod in agreement. He then tosses in some clothes and tells them to get dressed.

Matt had gotten so used to being naked all the time that the clothes felt weird. They then look at each other, and Matt knows that life will never be the same.

The End

Contents