I was cleaning out my garage, a dirty job, but one that needed done. I made my way to the stack of wood in the back corner. 
The wood was ruined; it had gotten wet and was rotted out. "Nasty…" I muttered as I carried a few pieces out at a time.
I moved the last piece and I jumped, dropping the piece off to the side. There was a little brown mouse who had been hiding behind the piece.
"Shit!" I exclaimed, a bit startled but not nearly as scared as the little guy huddled in the corner.
I could see his eyes were big, his chest was heaving up and down in fright and he was looking for a way to run.
I took a step back "Hey little guy, I'm not going to hurt you. Run away...be free"
He darted to the left, stopped, reversed and started to run right when all of a sudden, he stopped.
He froze. I watched his front shoulders hunch forward, his back haunches twitched, then they bulged out.
"What the heck?" I mumbled. 
The mouse stayed frozen as in not running but he was moving; he was growing. 
He was standard mouse size; about 6 inches long and no more than 2 inches high, but not anymore.
My heart began to pound. I was freaked out, fascinated and a bit afraid as the mouse grew to the size of a rat. Then, he kept growing. 
My eyes widened as he reached the size of a house cat. His body was growing proportionately, the tail grew longer, his ears and whiskers were very noticeable at this size. 
He reached the size of a medium dog. He hadn't moved an inch forward as his body had expanded. I watched in amazement as this tiny little creature had increased in size tenfold. His little feet weren't very little anymore. I saw details in his paws and claws and long pink tail.
At about 3 feet high, he moved and sat back on his haunches. The mouse shivered all over and looked at me.
I was frozen to my spot, flabbergasted. My jaw went up and down but no sound came out.
The mouse's jaw went up and down, a squeak and a chirp emerged followed by a chitter chatter sound. 
My heart was pounding in my chest and I was breathing fast. I wasn't afraid of a mouse, but a 3 feet tall, 75 pound mouse; that was a different story.
I went to take a step back but found that I couldn't move. I was stuck where I stood. I held my breath as the strangest sensation I had ever felt in my life washed over me. 
I felt warm, yet goosebumps broke out all over my body and every hair stood on end.
Then, my stomach flipped and began to rise like I was going down a roller coaster hill.
My eyes darted around and the most dreadful feeling hit me as I realized "I'm shrinking!"
"Ahhhh...AH!" escaped my mouth as I saw the walls around me growing higher.
Now, I'm a big guy at 6'3" and 220 pounds but a fixed object of a box on the shelf in front of me was moving. 
It started below my eyeline, came equal to, and then rose above me.
"What’s happening to me?!" I called out in a panic.
That's when I remembered my friend, the giant mouse in front of me.
I was quickly coming down to his size. My clothes grew big and loose on me. I could feel my feet shrinking in my shoes and my socks crinkling up inside them, my toes alternately lifting up and pressing down trying to hold on.
My jeans pooled up as my legs shrank down inside them. They slipped off my waist.
My arms pulled up into my sleeves and the neck of my shirt widened continuously as I got smaller and smaller.
My friend just stared at me, his little nose sniffed and his whiskers twitched as I shrank down closer to him.
Sitting on his haunches,  I finally stopped shrinking just a few inches taller than him.
"Oh my God….oh my God" I panted out as I finally came to a stop. My hands flew around patting down my diminished body.
I can’t describe what happened next except to say that the energy in the room changed. An electric charge seemed to pass over. The garage felt dry and filled with static electricity.
It got eerily quiet as I stood face to face with the mouse.
His front paws came up and he rubbed his nose and whiskers. His big brown eyes narrowed, it looked like he had an itch.
I couldn't believe my eyes; I thought they were playing tricks on me. I was obviously in shock but I watched as his whiskers pulled in getting shorter and shorter until the mouse simply no longer had whiskers poking out from alongside his nose.
That was when I felt an itch along the side of my nose and across my cheeks.
I scratched two times before I felt something poking out, something growing out, something firm, yet flexible. 
I could see them with my own eyes as they grew longer; more of them kept coming out. I could feel them as I ran my fingers over them.
I had whiskers.
I wanted to scream but found that I couldn't, I was too surprised. 
"Wow"
I jumped hearing another voice.
I looked around with my whiskers twitching "who...who said that?" 
"Oh. I guess I did...Wow! I can talk!"
I looked in front of me and the mouse was speaking. His expression has changed. He didn't look strictly like a mouse. His mouth was wider. His nose was flatter with larger nostrils. He looked like he had a brow line and could move his eyes differently. And he was speaking English to me.
"Yuh...yeah you can talk but how? Why?" I asked in a panic.
"I don't know" he replied "I don't know what is happening to either one of us. I was hiding. I could hear you but I was trapped and couldn't run. Then when I did run, I didn't get very far before I stopped. Then I got bigger and bigger...it was a weird feeling. Something told me to stop and stay. Then you came down to my size and, here we are"
I shook my head. I had just been lectured by a mouse. As I shook though, I felt something strange. My ears seemed to flop.
They felt hot and I could feel them moving, migrating up higher on my head. They grew huge in comparison to their usual size. 
I brought my hands up and touched the warm and soft flesh "Ah! My ears! Oh...oh no...if I've got whiskers...and I've got, I've got ears like you...and you're talking…" I drifted off.
"Are we switching places?!" The mouse asked excited "That means you'll be the mouse and I'll be the person! I'm going to be huge! And you’re going to be tiny...so small you can't even imagine it. Our bodies are changing into each other's!"
"No! I don't want to be a mouse!" I yelled feeling my nose pull out further as it shifted my mouth backwards. 
I saw his nose flatten and then build up into a human shaped nose. His mouth widened and I saw his teeth shifting and changing. 
The mouse's big ears shrank and lowered. I could see white around the brown in his eyes and as his fur began to recede, his cheeks and forehead, chin and jaw all started to take on a definite human look.
"Well I never wanted to be a mouse either. It's just what I was born as...but now I'm being made into a man and you're being made into a mouse"
"But I...that’s impossible!" I yelled as fur began to break out on my face. My pointed mouse nose twitched as fur covered it along with my cheeks and forehead. I could feel my eyes shifting and changing. My teeth were changing as my lips thinned. My chin and jaw pulled backwards. 
"Says who? It's happening to us" the mouse replied as he began to just have hair on top of his rounding head. "Why can't we switch species? I'm looking forward to becoming a human?"
"I don't want to be a mouse!" I yelled as I felt fur now beginning to break out all over my body. My shoulders rotated forward and my arms began to shrink.
"Now I guess it's just my turn to be human" the mouse shrugged as his shoulders widened and his fur receded leaving behind skin. His arms were growing and changing.
Another height shift hit us as my hips popped as did his but in the opposite direction. 
He grew 6 inches as I lost them. The mouse was now bigger and taller than me.
"Oh...I'm bigger! And I'm only going to get bigger while you continue to shrink smaller"
He put his paws out and watched them turn into hands. His claws pulled back into an fingernails as he developed thumbs. He stayed his fingers out wiggling and moving them all about, making fists, clenching and unclenching them. 
My arms were now furry and spindly and my hands were contracting into little paws with tiny claws. I lost flexibility in them yet retained some characteristics. I knew I could still hold thongs with them.
My body now shivered as it drastically changed shape and function.
My chest became long and straight. My hips shot outward and I lost my ability to stand on my legs, or my back legs as I was already starting to think of them as.
I fell forward as my back side built up changing into a mouse's. My feet elongated and turned into another set of paws also equipped with tiny claws. I felt the pads building up for traction.
My legs shifted size, shape, and dimensions "You need to…Squeak!" 
"Oh no! Oh shit! I lost my ability to talk! I thought. My mind was scrambled and panicking.
The mouse shifted how he was sitting as his hips shifted. He developed an ass and his chest rose up and outward.
His legs flipped and began to grow larger, their entire function changed and his muscles adapted to human needs.
His back paws were changing into feet and he wiggled his toes as they formed up.
My chest was heaving as my fur came in entirely.
He was naked and looked very human as opposed to me, who was almost entirely a mouse.
He grabbed his long pink tail "Still one thing left to swap. I can’t go around with a tail and you need this. You won't fully be a mouse without your tail"
"Squeak!" I let out as I felt it. A pressure built up at the base of my spine. "SQUEAK!" It popped out.
Starting off short and straight, it grew longer and longer, equal to my body in length. It was super flexible and I whipped it around in various directions showing my irritation.
He grimaced and clenched his muscles as his tail began to suck up into his body. It shrank up higher and closer until just a straight out nub stuck out. Then, with a shiver and a shake, it pulled in and vanished.
He looked over his shoulder and smirked.
"I'm you" he said looking at me "And you’re me haha...you're just a mouse!" 
Another shiver ran all the way through my body and I began to shrink again. 
He felt it too. He shivered and laughed and I saw him start to grow bigger in front of me.
Our size difference shifted very quickly. I was shrinking fast and he was growing just as rapidly.
His legs doubled in length along with his arms. His torso stretched out and he put his arms out wide as he now stood over 6 feet taller than me.
I was the size of a mouse.
I had shrank down to 6 inches long and 2 inches high. I weighed less than a pound. My pile of clothes towered next to me. Then I felt the earth shake as he took a few steps toward me.
I froze and quivered as he crouched down "Hey little guy...how does it feel to be me haha, cause I'm loving being you" 
His voice was louder than a jet taking off in a thunderstorm. His face alone was 10 times bigger than me. He stood back up to his full height as he grabbed my clothes. 
I looked up in absolute awe at his size.
He lifted a foot to put on my underwear and as it came back down, the shadow of it passed over me. With one step, he could crush me now.
The foot hit a foot away from me. I jumped. All four of my paws came off the ground with the impact of it.
He did it again with his other foot and I was lifted up a second time.
I stared at his toes. They seemed as high as me. I could look straight on at the end of his toes and see the lines where his nails were.
"Oh wow...everything looks so different at this size" he thundered.
I broke and ran.
I heard him laugh "Oh don't be scared little guy...I won't hurt you" but intook off, scampering as mouse instincts and muscles took over. 
I ran under the stairs that led up into the house where I found a crack in the wood and concrete and I squeezed up into a nook where I was protected. 
My heart pounded in my chest, my lungs heaved in fear. "This can't be happening! I have to be dreaming…wake up!"
I heard him coming. I felt his looming presence but couldn't see him.
"I don't know what to say to you...I didn't make this happen to us; I'm just as surprised about this as you are but I can't complain " he laughed "I sure you're mad as Hell getting turned into a helpless little mouse" 
He stomped off above me. I was too afraid to move. I slept a bit and watched as it got dark. 
My nose began to twitch and my stomach rumbled in hunger "Oh no…" I thought but I couldn't stop my mouse instincts now. 
I smelled food, something sweet and delicious was nearby and my little mouse paws started to move me.
I sniffed the air coming out of my hole. I didn't think I smelled a predator but I was still learning how to listen to these new impulses racing through my mind and body.
Cautiously I crept up in the dark. The smell got stronger and stronger. It was right there.
A piece of watermelon sat on the ground. Huge to my eyes, it looked like a full meal in chunk form. 
I sniffed then dashed out as fast as I could. 
I grabbed the huge chunk in my teeth and turned to run back when I felt a whoosh of air and then, I was in total darkness.
I dashed straight ahead and hot a wall. I ran another way and hit another. I was trapped!
A slight slit of light cracked at the bottom but as I scampered for it, something slid under my feet and I was lifted up into the air.
"Calm down in there little guy" I heard a thundering voice call out as I was bounced all over my cardboard cell.
The next thing I felt was warmth; I was inside my house and then I was dropping,, Fallin through the air.
I braced for impact, paws and legs out but what I landed on was soft, fluffy.
I smelled wood shavings. And food. And water.
I looked around. I was in an aquarium filled with stuffing and wood shavings. There was a ginormous bottle of water hanging off the side. There were food pellets and some lettuce and carrot chips along with watermelon.
I cringed as he put a lid down over the top of the tank.
"You could have stepped on me when I was in your place so now that I'm the big one and you're little, I'm going to take care of you. We may have switched places and had our lives reversed into each other's but don't worry" His big smiling face filled the other side of the glass.
A wheel was added the next day so I could run but it was the next day I got a really big surprise.
I heard more footsteps. I saw him and then my heart pounded as I saw her. My girlfriend Abby was standing over my tank smiling, leaning down, staring at me.
Her long blonde hair swung and swayed as she leaned forward. Then out of her pocket, she pulled out a small brown mouse. 
It squeaked but sat up in her hand as he opened up the top and put the mouse in with me.
I could smell her overpowering scent. Abby, the female mouse, the female mouse, Abby.
The other mouse sniffed towards me, then rushed over and curled up around me. Abby.
I ran to the glass and stood up, my little front paws pressed on the glass
"Yep! You're a smart little guy aren't you?!" She said to me. "Yeah...we swapped too! Isn't this great?! I was just a little mouse myself yesterday living under Abby's sink. Them, the next thing I know, I'm turning into her and she's turning into me!"
"You two have fun in there now" he said and the two humans walked away.
I looked at mouse Abby and she looked back at me "squeak?"