A simple transformation story. Not my best work, by far, but you don't improve by sitting down and complaining. You improve by sitting down and getting stuff posted, even if it's bad. Enjoy it.

Content warning: Transformation, of course.

The human waltzed his way into the forest, notepad and pencil out and about.
He stepped around the denseness of where he was, taking notes of this strange place.
“No dangerous pokemon so far… were the rumors false?”
Right after that comment, he wondered deeper… accidentally stepping on a branch with a CRUNCH.
The man panicked, looking from left to right, hoping he didn’t disturb anyone or anything…
Until he felt a crawling sensation on his right leg… looking down to see a venipede!
“Aaah! Get off of me!”
He wiggled his leg to no avail… it was committed to clinging onto him! At least until it delivered a Poison Sting right to his leg, before scurrying away!
“Owooch…”
The man quickly plopped against a tree and took off his backpack. He settled himself down for a moment, examining how he felt.
Another spurt of pain came to him. Knowing full well he was poisoned at this state… he quickly looked through his bag…
Five burn heals, four paralysis cures, three oran berries, and even an awakening and ice heal were in the bag’s medicine pocket.
“Ngh… this can’t be how I go out…”
He gathered his strength, lifting himself and the bag up…
…only to feel another pang of poison right through his leg, which made him collapse!
“I… HEEEEEEEEEEEEEEEEEEEEEEEEEEEEEELLLLLLLLLLLLLLLLLLLP!”
The cry of help that could rival even Luigi’s resulted in a flock of pidove fleeing the top of the forest! At least temporarily…
A few seconds later some intense rustling came… and the researcher held onto the roots his hands had fallen onto out of nervousness.
Eventually the rustler was revealed to be… a primarina?
“Ugh… whoever you are… the poison’s taking over my body… and if you can help me… that would be great…”
A grunt of pain came from the human, him not letting his eyes off the primarina either…
“Just… hurry… if you’re here to help…”
“I’ll try! Just stay calm and don’t exert yourself… it may make things worse.”
“Got it…”
The primarina reached into his secret stash… his hair…
And found absolutely nothing useful!
“Argh, I don’t have anything on me that could cure you!”
At this point, the human was weeping on the ground… obviously, not wanting to succumb to poison…
Meanwhile, the mermaid was thinking of how he could transform this situation from a bad one to at least a workable one.
The seal jolted up a bit. Transform! That was it… he could change the human into a pokemon… more specifically, a poison or steel type!
“I got it! I have an idea… but you may not like it!”
“As… long as it saves my hide…”
The primarina nodded, then focused! This may not be easy… and he knew he had to be fast.
No time to decide on a good pokemon either. Trusty #001 would have to do.
“Alright… stay still! Too much movement and you’d throw the spell off…”
The human simply stayed flopped on the ground, barely moving… almost appearing dead to the seal, who was breathing heavily at this point…
Eventually though, he focused his energy, and said a simple chant, just for good luck, and it helped him focus, too!
With what little energy he had left, the researcher writhed in pain…
But as time went on, that pain seemed to go away…
And go somewhere else! To his limbs, to his stomach… why was he green now?!
“W-what have you done to me?!”
“I know it’s crazy but… after a minute or two, the pain’s going to subside completely!”
“I don’t even know if I can bare 30 more seconds of this!”
“I sacrificed painlessness for speed to save your life! Just… try and bear with it for now!”
He grunted and nodded, gripping on the ground hard… his strength was returning!
But ow ow… why were his limbs becoming so darn stubby?!
He went from laying on the ground to a quadruped standing position… this began to feel much more natural to him, especially when his limbs reached an all time low.. .and seemed to stop reducing in size!
“This… isn’t so bad…”
A moment later, the human felt a huge pain on his back, at his chest, and on his head! His back felt like it was sprouting something huge… his chest was again adjusting in size, getting much smaller almost as if to adjust to his limbs!
And his head was becoming wide… his eyes and mouth spreading out, creating a near-indescribable pain that even made it hard to talk…
“Ohkay… nevhermind!”
“Just a few more seconds! You’re going to be alright!”
The primarina reassuringly rubbed on his sprout, which had come to be fully by now!
And he assisted him by speeding up the transformation on his tum, rubbing over it and giving it that classic bulbasaur spotted pattern, along with giving it to the arms and legs that had been missed earlier, too!
A few more seconds of painful face stretching, and ear adjustment and it had been done. The researcher was now a bulbasaur.
“What on earth did you do to me?”
He glanced at his stubby green arms, stretching them out and falling flat on his face! He stretched out his tongue a bit too, immediately recognizing what he was, but before he could say, the primarina told him!
“I panicked and made you a bulbasaur. It’s the first pokemon in the pokedex, and the first one that comes to mind! So, since you’re a poison-type… you’re now immune to poison, which means you shouldn’t feel it at all…”
The new grass-type nodded…
“That’s some pretty quick thinking…”
And then he angrily hopped on his little legs once!
“But if you could do that, why don’t you have a spell just for curing poison?!”
“I’m uh… working on it.”
Mako bashfully rubbed the back of his head…
“You see… being a fairy type I’ve sort of… postponed working with poison, meaning I haven’t really done a proper spell of it. And I also didn’t have a pecha berry or scarf so… sadly that was my only option!”
“Then couldn’t you turn me back already?! It should be gone by now, right?”
“Well… yes and no… it may still BE there, but you just don’t notice it, because poison-type. I’d suggest staying how you are til we get somewhere where there’s an antidote or two for you. Unless you’d rather take a risk at returning to how you were earlier.”
The bulby shivered, and shook his head!
“I-I’ll think I’ll pass… maybe this form has some advantages! Like… firsthand research!”
“That’s the spirit… being a pokemon really isn’t so bad.”
He patpat the bulb of the bulbasaur!
“You get a lot of things humans just, don’t have. But… I’m sure you have a life to return to, so I’ll gladly go ahead and escort you to wherever you need to be.”
The grass-type shook his head.
“No no… at least not for a good two weeks.”
“I guess your little uh… research collecting trip thing… is off to an interesting start then.”
And then the bulbasaur nodded a bit!
“This… I’m starting to like it a bit. So, maybe for these two weeks I’ll research what a pokemon feels like instead! It’s much more interesting then what I had planned…”
“Well, I’m glad to help out in that case, heh… much better than being dying on the ground from poison!”
“Agreed! But… can I get your name? If pokemon even have one?”
“It’s Mako.”
“Mako eh? Well thanks for your help again… without your… admittedly unconventional means, I’d probably be a goner by now… but just be sure to change me back when all this is said and done, alright?”
“Absolutely will do!”
The bulbasaur focused, and had vines come right out of his bulb, attempting to snatch up his pencil and notepad… even managing to write a bit!

A certain primarina who calls himself Mako helped me get a different perspective on this little research escapade. I’m sure it will provide one of my best trips yet… even though feel weirder than I ever have in my entire life…

Unfortunately for the ex-human, what he had just written was nearly illegible. When he would inevitably return to his human form, he would undoubtably have to rewrite every word for his colleagues… but nonetheless was happy to have a once in a life time chance such as this.