Since the author has decided to go in National Dex order (in case you forgot/don't know. The National Dex order for the Eeveelutions goes, Vaporeon, Jolteon, Flareon, Espeon, Umbreon, Leafeon, Glaceon and Sylveon), we'll be staring off with the Vaporeon's part first instead of the Flareon's part.
The truck that the Vaporeon had been loaded into had been on the road for awhile, and the Vaporeon was beginning to that he was never going to leave the box and that he'd be trapped in the box forever. He didn't want to risk breaking open the box and causing an alarm but at the same time, he didn't want to stuck inside the box.
"To leave or not to leave?" the Vaporeon thought.
Twenty hours later, the truck pulled to a halt in a neighbourhood. The employee took out the box that contained the Vaporeon and placed it on the doorstep, then he walked away to continue delivering the rest of the parcels.
The sound of footsteps walking away from the box was the Vaporeon's cue to escape. He busted open the top of the box and fled the doorstep.
"Free at last..." the Vaporeon sighed. "But, where am I?"
Unfamiliar with his new surroundings, the Vaporeon just ran out of town until he came across a college campus. Though hesitant, he decided to stay at the campus until he could get things figured out. That night, he ate some berries that grew near the pond and decided to sleep near the pond located at the campus.
The next day:
We now to cut to twenty two year old Eric Cartman. Cartman just woke up, he looked at his digital alarm clock to only realize that he had just overslept and that he'd missed his first class.
"Oh shit, goddammit!" Cartman exclaimed.
He rushed out of bed out of bed and got ready for the day, hoping that he'd be able to make it to his next class in time. Unfortunately, he arrived a few minutes late.
"Eric, you're late. Take a seat." the professor scolded.
"This is bullcrap!" Cartman bitched as he went over to his seat and sat down.
As the years went by, Cartman tried to change himself, he became less mean to his friends (even though he still teases Kyle for fun every now and then), shit, he even lost some weight over the years (even though he was still heftier than his friends) but he still couldn't really stop procrastinating and sleeping in.
Later when his classes ended, Cartman decided to go outside for a bit, hoping that maybe some fresh air would help. He brought a water bottle along with him just in case he needed some water.
"Stupid hippie professor..." Cartman groaned.
He stared at the pond in his campus, there was a ton of water type Pokemon inhabiting the pond. Cartman put his water bottle onto a flat stone nearby the pond. He then strolled around, looking at the various water type Pokemon.
The Vaporeon was still wandering around the college campus because he was still unsure about the current situation he was in.
"Glaceon? Espeon? Anyone?" he called.
Then, the Vaporeon noticed Cartman and spied on him from a distance. When Cartman sat down near the rock that his bottle was settled on, the Vaporeon used Acid Armour and hid inside Cartman's water bottle.
"Huh, who was that?" Cartman asked, looking around. "Water type Pokemon are so lame, why couldn't there be any fire types here?"
"Fuck these stupid wetlands, I'm going back to my dorm..." he groaned. "Why do I have to go here, why does that jew get to go to a university that has fire type Pokemon inhabiting there? We should trade places."
Cartman grabbed his water bottle and went back to to his dorm. Luckily (for the Vaporeon), Cartman didn't drink the water since he already took a few sips before he hid in the bottle. When he returned to his room, he just set his bottle on the counter (and he didn't bother screwing up the lid) and went straight to the TV.
The Vaporeon somehow managed to exit the bottle but in process of doing so, he caused a ruckus and spilt water everywhere! Cartman came to the kitchen to find a Vaporeon standing in the middle of a puddle.
"The fuck?" Cartman screamed.
"Vaporeon, vapour..." the Vaporeon shuddered.
"How did you enter here? Get out of here, you retarded fish cat thing. I want a Flareon, not you!"
Instantly, the Vaporeon melted into a puddle of water, increasing the size of the current puddle.
"Shit, I have to clean up this mess." Cartman moaned.
He was about to get some paper towels but before he could reach out and take some, he felt the urge to catch the Vaporeon and give him lots of TLC. Cartman calmed down and apologized to the Vaporeon for scaring him.
"I'm sorry for scaring you. You look so cute. Want to stay with me?" Cartman begged.
The Vaporeon was still spooked from Cartman screaming at him earlier but he eventually stopped shuddering when Cartman pulled out a Cheesy Poof. The Vaporeon reluctantly came closer to Cartman and took the Cheesy Poof from Cartman's hand.
"Good boy, now go inside the Pokeball." Cartman praised.
He pulled out a Pokeball and tapped it on the Vaporeon's forehead. The Pokeball opened, captured the Vaporeon and shook three times before making a "ping" sound, indicating that the Vaporeon had been captured. Cartman the opened the Pokeball and let out the Vaporeon.
"Now, what to name you?" Cartman wondered out loud. "How about Chris?"
The Vaporeon, now known as Chris, didn't understand who was Chris, so he didn't respond.
"Vaporeon?" said Chris. "Vaporeon, Vaporeon?"
"Come here Chris." Cartman coaxed.
Chris still didn't understand that his new name was Chris.
"Come here Chris."
No response.
"Chris."
Still no response.
"Stupid, bitch ass-" Cartman thought before something in his mind cut off this thought.
It took him several attempts for him to teach Chris his new name but he still managed to do so in the end. When he did learn his new name, Cartman gave him another Cheesy Poof.
"Now that's a good boy, Chris." Cartman said as he petted the Bubble Jet Pokemon's head.
"Vaporeon..." Chris said.
"I'm going to take a shower now, stay here and sleep." Cartman cooed.
He then got undressed and entered the shower.
"Sweet..." Cartman muttered.
As he showered, he felt something brush up against his leg. Cartman looked down to find that Chris had entered the bathroom and decided to accompany his new owner in the shower.
"No, Chris. Get out." Cartman reprimanded.
Chris sulked.
"Okay, you can stay since you love water." Cartman sighed and gave in.
"Vaporeon!" Chris exclaimed.
When Cartman finished taking his shower, he stepped out of the shower to dry himself off. Chris also left the shower and shook himself dry. Water splashed everywhere when he did so but he didn't seem to mind that his new Pokemon soaked his bathroom.
Later, Cartman was sleeping like a baby until he felt something under the covers.
"Ahhhhh! A monster is in my bed!" Cartman screamed.
"Vaporeon?" a voice spoke.
"Oh, it's you, Chris." Cartman sighed with relief when he lifted the bed covers, revealing that the creature under the covers was none other than Chris. "You gave me a fright. Now get off my bed..."
Chris didn't leave, he just fell asleep beside his new master.
"Fine, maybe just this night." Cartman gave in.
He then went back to sleep. As he slept, Cartman realized why he gave in with Chris instead of fighting back with him.
"Oh, so that's why I gave in. That was because I wanted a Pokemon, specifically an evolution of Eevee. I wanted a Flareon but then I remembered, Heidi is allergic to Flareon. I guess having a Vaporeon won't be so bad. Besides, he's better than my bad Glameow, Mr. Skitty."
Bonus:
Cartman was watching TV and Chris was sitting beside him on the couch. Cartman was eating some potato chips, Chris looked at Cartman, hoping that he'd give him a chip or two.
"No Chris, these are my potato chips." Cartman scolded.
"Vaporeon?" said Chris.
"No Chris, these are my chips!" Cartman bitched. "That's a bad-"
Before Cartman could continue yelling at the Bubble Jet Pokemon, he felt the urge to stop screaming and just give in with Chris.
"Okay, just one chip. Just one and no more." Cartman sighed.
He reached into the bag and fed Chris a chip. Chris crunched on the chip and swallowed it.
"Like it boy?" Cartman asked.
"Vaporeon!" Chris nodded.
Cartman then fed his Pokemon another potato chip, and another, and another, until the bag was empty.
"Oh, I'm all out. Sorry Chris." Cartman apologized.
"Vaporeon..." Chris snored.
"Sleep boy, I have to study." Cartman whispered as he got up from the couch and returned to his room.
Chris didn't respond, he was fast asleep.
A/N: I know Cartman was out of character in this part but, I guess he really did change over the years in this AU. Same goes with Chris, he's also acting out of character (normally, he's grumpy, tired and slightly cranky) but I'll try to avoid Chris from acting out of character in future stories.