I'd had the idea of a series of one-shots surrounding pokemon TF drinks, but didn't have a starting point until I asked my twitter followers for some TF prompts. This prompt was courtesy of, and the resulting story is a gift to,  Darkwolflord. Enjoy this wholesome willing TF tale!

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Wallace sat on his porch overlooking the extensive back woods on his rural property, sighing wistfully at the setting sun. Once, long ago, that wilderness beckoned him to the hectic and exciting life of a Pokemon trainer. He and Sprouts, his bulbasaur, went on many a strange and wonderful journey together, adventuring and battling their way across both Kanto and Johto. But then came the financial troubles, and the sudden death of a relative forcing him to abandon his dreams to care for the family business. The apartment he'd had to move into—already inferior to his preferred mobile lifestyle—had strict no-pokemon rules. And so it was with a heavy heart that Wallace parted ways with Sprouts, releasing his old friend into the wild. He knew that he had little choice—it wouldn't be fair to Sprouts to be cooped up in a pokeball 24-7, and simply passing him over to another trainer felt... wrong, somehow. Like he'd be selling a friend like a common trinket. Besides, the wilderness was home to both of them once, and he knew Sprouts would prefer that life to any other. Years had passed from that time; decades, even. It took quite a bit of work and effort over long, thankless hours, but eventually he'd managed to set his family business on even footing. Now a 75-year old retiree, Wallace spent his time in a home off a country road—the closest an old-timer like him could get to the wild places of his youth.

The last rays of daylight finally began to recede from the world. “Oh, to be young and full of energy again...” Wallace said as he carefully stood from his rocking chair, groaning a bit as he did so before moving indoors and sitting down again, this time in front of a TV. It seemed like all the energy he had these days was used up moving from one chair to another. “So, what's new in the world?”

The answers he got from the TV were not promising. Insipid “reality” shows. Talking heads yapping nonsensically about this or that subject. The latest celebrity scandal. All of it, bland and empty, and barely any change from the content (or lack thereof) from the day before.

“Why do I bother... huh?” A strange commercial had popped up and caught his attention just as he was about to switch the TV off:

“Lacking energy? Try new Poke-Power energy drinks, the only fuel a Pokemaniac needs!”

A mewlike mascot flew into the frame, glowing dust trailing in its wake and poofing several cans of energy drink into existence. “This all-natural, all-new, all-exciting formula will give you a boost unlike any you've ever had! Not only that, it comes in several amazing flavors!”

The mascot floated over to the cans, gesturing to them one by one; each can was a different color and had a different pokemon on the label. “Worried about weight but can't keep up in the gym? Then Machop Maximum could be the flavor for you! Need a spring in your step to speed up your life? Pikachu Pep has you covered!”

Wallace couldn't understand why, but something about the commercial seemed... trustworthy. Genuine. He shook his head. No, it's probably just as silly as any other trendy drink—

“Wanting a wilderness hike but too tired to travel? Bulbasaur Boost can help with that!”

Almost as if the program had tuned in to his own interests just as he began having second thoughts, the newest flavor on display tugged Wallace's focus back to the screen. Something about the bulbasaur displayed on the can sent waves of nostalgia through him, thoughts of Sprouts and all the adventures they'd had together. Heh, energy for a wilderness hike... like old times. May as well give it a shot.

“All these flavors and more, found at your local grocery store! Poke-Power energy drink: Pure Pokemon Power in your veins!”

The very next day, Wallace went to the grocery store to see if they had the new drink in stock; to his delight, they had plenty, and even had a sample station. A sip of the drink alone sent invigorating shivers down his spine, filling him with energy he hadn't felt in years. That was all it took for him to buy a six-pack of the bulbasaur flavor and prepare for a short camping trip in the woods. The sample cup lasted him a few hours before wearing off, and rather than a crash like with other energy drinks there was a pleasantly slow descent to a state of relaxation rather than exhaustion. Plenty of time for him to gather his things and begin his journey, the first in decades.

As he trudged through the woods—already feeling ages younger as he occasionally took one of the cans and drank from it—Wallace's thoughts turned once again to Sprouts. Pokemon of the Bulbasaur line could be quite long-lived, some reaching ages of hundreds of years. Perhaps his old friend was out there, still young and lively... the thought brought a smile to Wallace's face. “Ah, my dear friend, at least you won't have to worry about your back aching every rainy day until a few centuries from now!”

Almost on cue, a strange itch on the small of his back caught his attention. “Oof, that's going to drive me nuts...” He stretched and twisted, but the itch proved to be beyond his feeble reach; fortunately, it passed as his energy boost slowly began to dim down again. As he stumbled across a clearing with a small brook trickling through, Wallace decided to pitch his tent and sit around enjoying nature for a while. In spite of his relaxation, he found himself continuing to sip from the drink occasionally. Suddenly, a new annoying itch popped up on his forearm, along with the one on his back; looking down to start scratching his arm, Wallace found himself staring in shock.

Green scales were forming along the itch lines. His fingers were slightly shortened, though still somewhat dexterous, with claw-like protrusions at the end of each finger. No sooner had he noticed this than the itch on his back changed to a feeling of something pressing against his shirt; it didn't take long for him to put together what was happening.

“Am I... am I turning into a bulbasaur?”

“Venusaur, actually,” a new voice chimed in from overhead. Wallace looked up to see a pink catlike figure floating overhead, smirking at him. “Enjoying my product so far, I take it?”

“Y-you're Mew! Wait, no, this has to be a dream—”

Mew giggled as they twirled in the air. “Nope nope nope! Aaall real! But totally reversible... as long as you don't drink any more.”

“But I only managed to get out this far because of the energy boost! I can't get back home safely without it!”

“Aw, don't give me that,” Mew responded with a dismissive wave. “You never really thought of that old place as your home, at least not to the extent that the wilderness was when you were young. And before you try denying it, remember that I'm psychic. And omnipotent.”

The old man in question shut his mouth for a few moments as he tried to process what was happening. Looking down at his arm, he saw the scales receding in time with the energy boost wearing off. “Well, I'll be... the things youngsters can think of today.”

“You can call me youngster when you pass two thousand years old, 'kiddo'.”

“Fair enough,” Wallace responded; “but the fact remains that you've put an elderly human in a rather tricky situation. I'm too feeble to survive out here on my own for an extended period of time, but I don't quite think I'm eager to no longer be human. At the same time, though, without your little drink, I can't safely get back to the house, which means I either choose to starve or am forced to permanently take a new form.”

Mew flipped upside-down and stared at him with a curious expression. “But think of it! You'll live way longer—the change will add literally centuries to your lifespan, you'll feel stronger and more energetic, and you'll be happier out here than you ever...” Their face fell. “Ah. I see your point. I suppose I didn't really give you much of a choice in the matter... okay then! Here's what I'll do. I'll give you a full two day's worth of energy to spare, no transformation, no drinks needed. That should be plenty to get you back, if you choose to go on being a boring old human.”

“And in exchange for this?”

“Just that you take some time to consider the offer I've given you. Spend the night here at camp, think it over, and if you want to stay human? Just walk away. If you change your mind, though...” Mew floated over to the remaining cans of drink and waved their paws over them; the drinks became a single can, glowing faintly. “...drink this, and you'll change permanently. So what'll it be? The same old boring, bland, tedious life of rocking chairs and bad TV of an old human in his twilight years... or a second chance at adventure and excitement, in the wilds where you feel truly alive?”

Wallace found himself struggling with the decision. “I'll have to think about it...”

“Alrighty, then,” the catlike psychic chuckled as they faded in a burst of sparkles. “Have fun!”

With the new revelations in mind, Wallace sat down on his camping stool to think. True to Mew's word, he felt the energy coming back to him, minus the scales; and yet, something about their words kept him rooted. As he sat in thought, however, he was startled by motion in some nearby brush; before he could flee, an ivysaur trotted into the clearing. But not just any ivysaur. The markings on the snout, the canny look in the eyes, the telltale mark on the left ear; evolved or not, there was no forgetting a face.

“Sprouts? Is that you?”

“Ivy? Ivysaur saur!”

The pokemon smiled and bounced happily, confirming Wallace's suspicions. To his amazement, however, he found himself fully able to understand his old friend's speech. “Incredible... oh, my good and wonderful friend, time has been a lot kinder to you than it has to me!”

Sprouts frowned and tilted his head. “Saur saur?”

“Oh, just age. I'm afraid we humans don't last as long as you do...” Wallace sighed. “To tell you the truth, Sprouts, I never stopped thinking about you. Not once. You don't resent me for letting you go, do you?”

“Ivy,” Sprouts responded with a shake of the head. “saur ivysaur.”

Wallace laughed a bit. “Haha! I'm glad you're happy out here. You deserved better. I only wish I could have joined you back then.”

That stopped him in his tracks. Wait, the only reason I didn't was because of my obligations. I'm retired now; I have no further obligations. I'm free to do what I want...

“Sprouts... would you believe me if I said Mew was here a few minutes ago?”

“Ivysaur ivy!”

“Wait,” Wallace said with mild surprise, “You saw that? Well, then, I guess I don't have to explain it all to you. But I don't know the first thing about being a pokemon.”

The grass type strode over to him and nuzzled him. “Saur... saur saur.”

“Well, I guess there are worse teachers. You certainly taught plenty of challengers a lesson or two back in the day!” The pair shared a brief laugh before Wallace's gaze floated back to the drink. “You know, I think I'm quite ready for another adventure!”

Opening the softly glowing can and drinking the contents in one go, Wallace felt the effects coming on almost immediately. The itching came back, but as the scales spread and the flower on his back began to form it thankfully faded into a pleasant tingle. He could feel his clothes begin to strain as he gained size and girth, and the shifting of joints quickly forced him to all fours. Twin feelings of pressure on his face and his backside were quickly followed by stretching sensations as his nose and mouth lengthened into a snout and his tailbone grew into a short tail. Already his hands and feet were losing dexterity as his fingers and toes fused, locking him into a permanent quadrupedal gait. At last, his clothes could take no more, and burst apart just as the massive flower on his back unfolded in full bloom.

“Ivy saur!” Looking good!

“Venus ven saur venusaur. Saur saur!” Thanks, old friend. Adventure awaits!

With no regrets, the two companions wandered off into the wilderness as a giggling form watched from above.

“Another happy customer!”