A quiet time at your parents' place leaves boredom to take over. At the guest house, you're laying about on the bed. I'm at the house getting cleaned up. After a few minutes, you're eyeing an open metal container. Opening it, you take a gander at the impressive collection of potions, salves, and tinctures. With me unable to administer something, you're free to explore on your devices.

Exploring, you take a whiff at one of the potions. You're repulsed at the smell of stale soda. Away from the container, you go into my book bag. Behind a glass box, you find a dark purple potion housed in a translucent conch shell with a rubber top. A sticky note is on it, saying "Unstable batch. Do not use on Lab Rat."

Anger swells inside of you. How could I identify you as a lab rat? It's unclear if the note is targeted for you, or for actual rats used for testing. You set aside the anger to explore the potion more. 

You open the rubber top, and take a whiff. It smells heavenly in comparison to the other potions down there- grape cotton candy. On the rubber stopper, it's printed PSY02150. You bring it close to your nose, enjoying the smell. It grows on you, almost... Intoxicating. 

You take a sip, and you become instantly addicted. Drool slides out of the corner of your mouth. You wolf down the potion, putting caution to the wind. The smell of the grape is strong, feeling heavenly as the taste can't be ignored. You down the rest of the potion, sucking it dry. Probing your tongue into the bottle, just the essence of the potion drives you bigger than yourself. Something is giving you ideas. 

How could you be some simple lab rat? No, you're more than that. Far greater. Why can't you force me to make potions for you to become magnificent beasts? You start to grin, these thoughts liberating you from the norm. A sharp pain brings your attention to why are you thinking like this. Is this really you? The momentary confusion makes you drop the container onto the glass box.

The force is more than enough to shatter the glass. As it shatters, you hear movement coming from outside. In 30 seconds flat, I kick open the doorway, aiming a stun gun to you. Silent on approach, I advance just enough to close the door behind me. A black bathrobe covers most of my wet body. I'm mad. You hear my thoughts, as I am too furious to speak.

Out of all of the potions to down, you had to pick the one I was going to test when I caught some field mice and use it on them.

You are aware that I came in running. All too well you sensed me barging in. You find my thoughts, disarming the stun gun with your force of will. It floats out of my hands, and you fling it to the other side of the room with telekinesis. A smirk is quite wide as your eyes have taken on a purple hue. This doesn't look promising.

Nuts. I hoped that potion just broke due to laziness, not by you snooping around and downing it. Superhuman reflexes. Extra-sensory abilities. You drank it. 

"Easy now... I heard a crash and was ready for the worst. I'm thankful it's you." 
I then raise my hands to open palms, surrendering, showing my intent. Unfortunately, you don't see it that way. 

"Why should I believe you!" You shout, revealing sharper teeth as you are seething. 

Your skin pales, losing their human complexion. It darkens, turning to a faint light violet. Are you aware of what's happening? 

"Hey man, I know this isn't you. We joked that you're my guinea pig, remember? The giddyness as you went part Vaporeon? Sneasel? Lugia? Please. Listen to reason." 

That pokemon side is struggling for control. Without memories to recall, the other self wants to be dominant. 

"Guinea pig, eh? I know my place! I'm stronger than you! So much...NNNGH!" 

A sharp pain pierces the back of your head- a thick cable of flesh connecting the back of your head to your spine. Through your hair, bony flat horns rise upward. You smile as you feel a surge of energy. Your eyes glow a deep purple, not looking human at all. With you on a roll to get my head to roll, I have to try and calm you down.

I know that I imagined hostile situations, but not like this. While I think quickly on what to say, you look behind yourself at a bulge. It swells, feeling warm against your skin. Thrashing against the seat of your pants, it's uncomfortable. I try and level with you as you feel something poking above your rear.

"Yeah? You drank my sample. My ONLY sample. That potion lasts for maybe 2 hours. I don't know. It's untested. What are you gonna do then?" 

Can't deny my fear. I have to do something as a gesture of goodwill. You're my friend, even with that rough exterior. I look a little sad, glancing down to the ground. Your spine explodes, endorphins breaking through to register the change as good, as the thick edge of the deep purple tail curls outward, trying to break free.

Moans come out of your lips as it feels good to change. The tail feels great as your legs creak, bones cracking to spread your stance outward. You groan and find a hand reaching down, stroking the new deep purple skin. While on the throes of comfort, the other self responds to the threat of losing the feelings.

"Nnnngh. You're lying! You're just trying to scare me!" 

From behind, your new tail thrashes, thickening outward while growing longer into your leg. Your face pushes out ever so slightly into a rigid snout, groaning with your tongue hanging out. The changes move to take a hold of your hands.

Fingers pair up, merging together to thick, rounded fingers. Thick pads press out of your fingertips. There's no sign of fingernails with three fingers looking identical in each hand. Something dawns on me as your omnipotent will is shaken by my threat.

Can you not read me to question what I am saying? I move to stand before you. Wider hips wiggle as your tail tries to break free. I approach you, thinking I can make this situation better. 

"Here, let me help you..." 

Moving my hands to your rump, I sink my hands under your pants. Feeling the base of your tail, it cracks as tired muscles are offered some relief. I move my hands to the hole, tearing it open with very human grips. You moan, sighing at the relief as your tail slides out of the hole, instead of bunching in those pants. Underneath, your sneakers are getting tight. Those toes are ballooning, making creases to the front of your shoes.

You bellow out a shudder as your hands dig at the shoes, feet trying to expand. Just above where the sneakers are on your feet, I see your ankles, swelling to large baseballs, sliding your feet away from the footwear slightly. This only helps bring more pressure to your toe area. Those feet are growing, moving to bust outward. Bringing my hands down your legs, I don't notice your stomach expanding, growing firm against your shirt. The dark purple growth forming there connects to your tail. Pulling the socks down, I see the ankles adjusting, raising your feet to be arched. Clearly the focus of demanding leadership is suppressed while helping you feel your changes.

"Hey... Hey, your feet are changing some... Do you mind if you want to stand on the couch? And err... Let your feet rip your sneakers apart?"

"S...sure..." 

As you agree, you look down at me with eyes growing taller, replacing the human oval eye sockets to angular trapezoids. You move to the couch, gasping as your tail curls against your new hands, softer fingers rubbing it deeply. With free reign of control, you shout as the tail curls around your midsection, tearing it apart. Your toes clench as tight as they can, feeling the pants start to fall clear from your shorts.

Taking a hold of the tattered pants, I pull them away from your body. The tail looks really strong as your legs are apart as a result. Seeing you stand before me... Bit menacing as the situation we got through has me sweat lightly. That, or my damp hair is from the interrupted shower. I see the ends of your shoes split from the front, seeing white socked feet spill out of the manmade materials. Bringing my hands to pet your feet, I rub them, socks starting to rip. 

"Ah, growing nicely... Gonna be too big for these shoes..."

The large toes squirm under the socks as you lean back and gasp at the suddenly release of the tips of the toes. They lack any trace of nails. I see them curl as you groan and feel your hands rubbing at them, rounded fingertips helping to rend the materials. Clearly you wanted the bindings free as much as I do.

"Nnnnngh...!" 

I blink, letting some time pass as I see the expanding feet, bunching up your socks. Soon, your feet are wide, catching the shoes inside your growing feet. The edge of your toes press against the cotton socks. The five toes at the end of your socks start to meld together, making two wide toes that tear the socks ever so slowly. Your large feet and ankles split the sneakers apart, clean for you to step and press onto them. Throwing your head back, you close your eyes, releasing a hiss of relief. Hey, might as well push my luck with your current state. 

"Hey, up for focusing on your feet?"

"Nnngh...so...so you...yes...s...sure..." 

A daze washes over you, burying hostility. Compliant, you gasp as the toes, easily a few inches wide and long, easily pulling and ripping the sneakers. Light violet skin is exposed to the air as the fabric covering them finally rip apart. It leaves your feet free to arch as high as they can, 18 inches wide and 4 feet long.

"Yes, focus on those feet... They look magnificent... large, growing, showing them off, taking about them..." 

It would seem that control is seated to my hands. Whew. I bring my hands over to your knees, feeling your legs growing longer, thighs bulging with muscle. Pressing into your knees, they snap. Further inward, the knees return, but pressing behind you, reversed. Looking at you all over, you're finished changing. Awesome.

<...thought I was completely out of it, did you?> 

Crap. I hear you in my head. 

<Now then. I'm in charge now!>

Anticipating the worst, I close my eyes, bracing myself for the unknown of your other self to do some damage. I feel my body floating to the sky, turned onto my back. Then, I feel the comfort of cushions. The couch? Warmth spreads from my sides, then my legs as you sit down on them. I open my eyes, and find part of your feet rubbing at my sides. How unique that your other self is around but to a relaxed state. Is it reassurance that my fears can be laid to rest?

<I'll make sure you enjoy this!>

Can't help but wonder how this is going to turn out. With the suggestion of having you focus on your feet, showing and talking about them, in such a way, I try to roll with it. I let my right hand rest on your left foot, wrapped around my side. It's a firm grip against me, but not hurting me. I raise your right foot up. It strokes my cheek, moving to press down onto of my head. Like this, I bring a hand to each of your massive feet, finding any skin to touch and rub down. Your groans sound great to my ears. 
The mood slips, and you're aware enough to have an inch that needs to be scratched.

<Hey. Can you do something for me?>

"Suppose I can. Next time, easy with the potions on your own?"

<Noted. But while I am like this, I require something to help these wonderful feelings.>

Feelings? Of what? It doesn't take long as you speak to me as I peer over to your 8 foot long tail.

<Yeeeeeeesss... My... My tail... I want to feel something rubbing it.>

You whimper as the thick tail sways behind you. 

"Sure. Flip around. Bend your knees so your feet are pressing to my sides. I'll feel up your tail if that's what you desire."

You groan, nodding as you're eager for some tail play. Moving to position, you shiver and sigh, revealing your massive soles. You arch your tail upward, giving me access to it.

How would this work? I start at the edge of your tail, it twitching at the anticipation of being touched by outside hands. I get right at it, pressing my palms at the end of the little curl. Odd, it feels funny at first, reminiscent of rubber. I press forward. It takes a moment to regain control, holding it in both hands. I move further, getting my way to the thickest part of your tail. Your tail arches, gasping for air at the feelings. The hands keep working, feeling the rigid tail up and down, rubbing harder up and down. After you moan and groan for awhile, I dig deeper, moving down lower to feel the meaty part of your tail- the thickest part of it. Gripping it causes you to squirm, unable to think straight as good feelings flood your body.

You start panting, growing louder the more I rub. The rubbery tail is smooth when not grasped, but easily gives way with my close contact. You move your hips, wanting your tail to sway wildly, but holding onto control so I can reach where you can't. I hear you moan, your voice sounding lower than before.

"Grrrr... Mmmm.... Mmmmmeeewwwwwwww..."

Time to amp things up. Meaning business, I push you forward. You fall down onto your hands, you turning your head to see what is happening. Most of my hands rest onto the firm skin of your back, not touching your tail. Your eyes glow purple, hiding your eyes, defensive at what I just did. I want you to grow ever so weary, craving that touch. For this instance, I am teasing you.

Just as your other self would force its way out of you, bliss fills your body. The sound of squeaking rubber fills your ears as my hands get back in contact with the rest of your body. My thumbs rub at the base of your tail on each side, digging deep to the rubbery skin covering weary muscles. I let my thumbs get company with my other fingers, probing at that spot. Naturally, you react to this stimuli.

"M... Meeeewwwwww... T...twwwwwOOOOOGH!"

I wonder how I can keep up to your eager demand. To rub is a heck of a tiring task. Your tail must be 3 feet thick at my hands. Thick and grand, it takes some time to get every square inch of it rubbed well. Your tail squeezes against itself, adding to the weakening rubs that I am applying. With the throes of pleasure at its peak and my energy dwindling down, I lay down to the couch.

You slide your toes underneath my head, wanting me to relax as I help you. I turn my head to the side, feeling the soft wrinkles of your soles warm up. You lean forward, resting your head on your arms, head turned to the side so we could see each other. My hands work your tail softly, petting it like a cat. All of the excitement is leaving us tired.

<You're sleepy? Ah it's fine... Just rub away a little bit more. Have a good nap.>

We catch some shuteye, past a bout of frustration and finding relaxation.