"Twilight, are you sure this is a good idea?" I ask, bringing my hoof up to my forehead and shaking my head. "I don't think you should be doing this..."
"It's perfectly alright, I've calculated everything that could go wrong and made sure to protect against them." She looks over to me, "Really, everything will be fine."
I hesitantly nod my head and resign myself to her judgement on the matter. I wasn't any good at chemistry in school and decide it's best to not argue with the mare holding the beaker in her magic.
"What are you making anyway?" I ask, unsure to why she called me down on my day off. If she was going to do tests again...
"I'm making a new serum to help mares with some... delicate issues during conception." Twilight turns around and gives a pleading look, "I need to test the effects on a mare and who better than my fillyfriend!"
I look at her with a "are you kidding" look and back up slowly, "No way, not after last time!"
"What, it only took you a couple of weeks to grow your mane back!" She says, moving towards me with a sly grin. "I'm your Princess, you have to obey me."
"Really, again?"
She stops and looks down, her ears folding back, "How about being my fillyfriend, doesn't that mean anything to you..."
I sigh, knowing I have already lost and walk towards her, "Give it here..." She passes the beaker to me and I take it in my hooves. The swirling mass of colours grabs my attention, but I shake my head, no point in wondering now.
With a small amount of trepidation, I bring the beaker to my lips and push the thought of this going wrong to the back of my mind as the liquid passes over my tongue and down my throat.
Mmm, tangy, I think as I lick my lips. Placing the beaker down, Twilight picks it up and returns it to the desk.
She brings out a notepad and a pencil. Sitting in front of me, she writes something down and scans me for any changes. A few minutes pass by with nothing happening, she gets irritated and frowns, "Something should have happened by now..."
"I'm sure it will, give it time... whatever it is." I start to feel something change within me as a small tingling sensation starts to flow over my hooves and up my legs making me feel full of energy.
"Uh, Twi honey... I feel something," I say as the tingling flows down my body. "Is it meant to so this?"
"Do what? What does it do?" She asks, excited something was happening at last. "What does it feel like?"
"It's a strange tingling... Things normal, right?"
"Um... Sure..."
"You do know what it's going to do, don't you?" I ask, tapping my hoof on the floor. Due to the energy now coursing through my body, I can't help but twitch. By now, the tingling had reached my lower body and was passing over my plot and marehood.
Twilight looks away, blushing, "Not entirely, I was so excited that the Princess asked me to have, I forgot to really check..."
Pushing it out of my mind, I close my eyes and exhale as my clit tingles. Twilight rushes forward, throwing the clipboard away and places a hoof on my shoulder, "Is everything alright, does it hurt?"
I open my eyes and look into hers, "I'm fine, and it’s just... nice." I say, feeling more confident all of a sudden. I find myself smiling as I place a hoof on her cheek, "I love you, Twilight."
She blushes and leans into my hoof, "Is this part of the serum?" She asks, smiling.
"No, I don't say it enough..." I shut my eyes as a wave of pleasure pages over me, making me fall forwards onto Twilight.
"Ah!" She shouts as she's pushed onto her back. She tries to get up, but finds me on top of her, pinning her down.
I breathe slowly. It feels like my skin is on fire where Twilight's in contact with me and I instinctively try and touch more. I feel a fire down below and some sort of pressure relief itself as a soft "squelch" sounds out.
Curious, I push myself up and look back. My eyes go open as I see, swinging between my back legs, a large erection. "Oh..." I mumble as I a soft breeze from upstairs pages over it, causing it to twitch.
I'm pretty sure I still had my vagina, the only thing that the potion added was that meat pole. Surprisingly, I find myself in awe; sure it wasn't the largest, but it was pretty respectable.
I look towards Twilight and see that she's looking up at me, "It seems to have stopped," I say.
"Yeah," she replied, her voice low. She looks down at my member and then back up, "How does it feel?"
"Weird and heavy..."
"I bet, it's pretty big." She brushed some hair out of my face and kisses me, "How about we test it out, for science?"
I lean down and press my lips to hers again, pushing against her. I feel my new appendage twitch in response and grow harder at the thought of making love to my princess.
I lower myself down and feel my cock as it rubs against Twilight's stomach. She smiles and kisses me one last time before pulling away.
"You seem tense?" She says, reaching down and feeling my cock.
I close my eyes and gasp as she rubs the head. "Twilight, please..."
"Seems you like th-" she's cut off as I release, spraying both of our stomachs and chests with warm, sticky jizz. She looks down and chuckles, "I guess that was to be expected..."
I can't help but look away with a blush, "Sorry."
She moves my face and looks me in the eyes, "Don't be, you only had it for a couple of minutes, I'll be more gentle." she kisses me on the nose nuzzled my cheek, "Where were we, oh yeah!"
She scoops up some of my own cum and licks it off her hoof. I tentatively wait for her to say something...
"Hmm, tangy."
I laugh and lick a little bit off her hoof as well and nod as she was indeed right. "I guess this was a success?"
"Oh yes, I would say so..." she replies, looking up at me with half-lidded eyes, "Now, I get to test you all day."
She teleport us up to her bedroom. We fall down and bounce on her bed. She lands on top of me and leans up, her pussy on top of my rapidly hardening dick.
She gasps and bites her lip as she grinds against it. "Who knew science could be so sexy..." she mumbles, rubbing my chest with her hooves. “Giddy up, pony!"
She moans and moves my dick with her magic, making me shiver in delight as it makes it tingle. Twilight greedily slurps up more jizz and slips the head of my cock into herself.
My cock pushes her folds out of the way as she moans like she's in heat. I instinctively buck my hips, trying to push even a little bit more of myself into her warm, moist pussy. It doesn't work as she's got the perfect grip on me and achingly descends on me inch by inch, teasing me.
I let out an unladylike grunt, grab a hold of her and spin around so she's under me again. She cries out but offers to resistance. She leans up and whispered in my ear, "Fuck me, stud."
I lose it and push the full length of myself into her, making her moan in my ear. This spurs me on and soon I'm finding a rhythm. I speed up our fucking and soon enough find myself close to orgasm.
I try and hold on as long as I can to give her a chance to come first and notice her walls start to tighten around me.
Her screams rise as I try for one last push. I hilt myself in her and come, spraying her walls with my seed.
Her walls tighten one last time and she tenses up. Screaming in ecstasy, she wraps her legs around me and nuzzled my neck, shaking as she comes down from her orgasm.
I continue to pound her as her walls milk me for all my worth. Soon there's enough seed to dribble out and pool on the sheers beneath her.
I pull my rapidly shrinking penis out and fall beside her. She turns over and cuddles up to me, moving my foreleg so she's comfortable. "That was something..." she whispers, her voice a bit hoarse from screaming.
"Yeah, it was," I reply, kissing her on the head. "I hope you have more of that potion."
"No, that was it...”
I look at her disappointed, "Oh, that's ok. I guess this was a one ti-"
She interrupts me by placing a hoof on my lips, "I can make more."
I look at her and she takes her hoof away. I smile and look down as my member shrinks back down and turns back into my clit. "I would like that," I say, grinning.