People born with dwarfism, though rare, are a lot more common than people born with gigantism. As the name suggests, people with gigantism have the opposite problem as people with dwarfism. Their bodies produced far more growth hormone than the average person, putting them well above other people in height. Even as kids, they would quickly outgrow their peers and probably their own parents. People can become as tall as 9 feet.
However, gigantism was living proof that bigger isn't always better. Most giants had trouble with their hearts. There was simply too much body for their hearts to pump blood all the way through. Their skeletons also suffered from having to carry too much mass on stretched-out bones. The life expectancy of a giant was not as long as a normal person's as a result.
That was why Lenny came to Animalia. He had problems with heart palpitations for years. Thankfully, he's been able to keep himself alive, but the change of government was threatening health care. So when he sent a letter to Horizon Lab asking for help, he was greatly relieved that they responded and told him to come. Lenny had no qualms about not being human anymore. Especially since there was a growing community that would welcome him.
Most people would have expected Lenny to choose to be blended with a species of megafauna, something like a bear or an elephant. But people who knew Lenny knew he was actually a, well-named, gentle giant. He always took care not to hurt anyone and anything around him. He had a softness for smaller creatures, holding them gently in his huge hands. So while it was a surprise to many, it was no surprise to other that Lenny specifically requested to converted into a mouse. But mice did have efficient hearts that powered their bodies and their bones were actually very flexible, allowing them to squeeze into so many spaced. So a mouse wouldn't be such a bad option for Lenny.
Lenny didn't really need to change out of his clothes when he got to the examination room. He doubted he could grow any larger than he was now and he had no illusions that just becoming a mouse will make him smaller. Biological growth is a one-way trip, there is simply no way to lose mass. He did take off his shoes as he doubted his paws would feel comfortable with them. Not that he would needs shoes after this.
Presently, one of the scientist walked into the room. He was followed by a lovely young mouse woman. She had soft grey fur and long chestnut hair. She was very admirably built with lithe feminine muscles and resplendent curves. She was also a little taller than the scientist, but not by much and certainly not as big as Lenny.
"Lenny, this is Milly," said the scientist, "She'll be your donor."
"Hi, how are you?" asked Milly. She had a pleasant enough voice.
"Howdy," said Lenny with his slow Southern drawl, "I don't have to kiss her or anything, do I?"
"Not unless you want to," said Milly coquettishly.
"We've been making dermal patches that are just as effective," said the scientist, "We'll start you on a single dose until we're sure your body has adjusted." Lenny obediently held out an arm and allowed the scientist to affix a dermal patch. Lenny swore he could feel his skin tickle as soon as the patch went in place.
They didn't have to wait long for results. Grey fur soon started appearing over his skin. Though not on his hands. They grew much pinker than before and his nails extended a little, but they didn't change that much. Though his feet did grow a little as they changed into pink paws. The worst discomfort was when his new tail started growing out from his backside, but that wasn't too bad. His face pushing forward into a mouse's didn't hurt a lot, but it did made it hard to see straight for a minute. His new whiskers tickled his nose a lot. He felt his new ears. They weren't nearly as big as he thought they'd get, but that wasn't so bad.
"How are you feeling?" asked the scientist.
"Like I ate that mouse potion from 'The Witches'," said Lenny, "But at least I'm not shrinking. I'm not, am I?"
"That shouldn't happen," said the scientist, "Well, there are cases of Animalians being smaller than they started out, but that applies to larger animals being uplifted, like giraffes and orcas. But how does your heart feel?"
Lenny placed a hand on his chest and felt it for a minute. "I think it's beating faster. It might be just because I'm excited."
"Mice do have a faster heart rate than humans," said the scientist, "But I think we should keep you here for a few days until we've determined your circulatory and skeletal systems are able to cope with your new physique. If it looks like there may be trouble, we can try a second dose."
"You don't mind if I stay around, do you?" asked Milly.
"Oh, not a bit, at least not as long as Lenny approves," said the scientist, "Excuse me, I need to get the fluoroscope prepared." With that, he left.
When the scientist had gone, Lenny turned to Milly and said, "So, if you're gonna stick around, tell me about yourself."
"Well, I suppose I should upfront and honest," said Milly, "I'm actually only three years old."
Lenny blinked before remembering that mice matured a lot faster than humans. "Well, you were a full-grown mouse before you were changed," said Lenny.
"Uh, no, I wasn't," said Milly, "I was actually human first."
"What?" asked Lenny in disbelief.
Milly brushed her hair and said, "Only former humans have hair like this. Manes come close, but that's far as it gets. I suppose you were told that a second dose of the virus causes anyone to age up or down until they're in their primes."
Lenny struggled hard to keep his jaw from dropping. "Wait, did they test that on you?" he asked.
"Oh, no, no, it was actually an accident," said Milly, "When the first outbreak happened, my family all got infected, but we were ok and we only got infected once. My mom didn't care a lot for breastfeeding, so she gave me bottles of milk instead. She got most of the milk at the Brown farm, but I guess she accidentally got an unpasteurized milk container by accident. One moment, I was sucking on a bottle. The next, I was fast-forwarding through childhood and puberty."
"Huh, you speak well for someone who's only three years old," said Lenny.
"I know. The scientist think that since my brain was still underdeveloped, the virus interpreted it as me still being like an animal. So it gave me a big neurological upgrade like other uplifted animals so I wouldn't have a baby's mind in an adult body," said Milly.
"And how did your parents deal with that?" asked Lenny.
"Obvious shock, but we're still close. To be honest, Myrtle's more like a sister to me than a mother. But I guess they really missed having a baby around the house because they started trying to get Myrtle pregnant again as soon as they could." Lenny gave her a shocked look. "Oh, don't be surprised," said Milly, "I might have been in the world as long, but I know how it works. There are uplifted Animalians who are younger than me and they had no trouble learning how to think and reason."
"So, what do you do with yourself?" asked Lenny.
"I'm a student at the Modeling School. Going through regular school would have been so tedious for me. I guess I technically count as a high school student, but it won't be long before I earn my G.E.D.," said Milly.
"Wow, you must be really above average," said Lenny.
"The scientists think I have a higher IQ because of the way I got a double dose," said Milly, "I suppose I was sort of the first case of the Animalia Virus being tested on an underdeveloped brain. They've been testing it with people who are a lot older than me but have more damaged brains. From what I hear, it's making good progress."
Lenny found himself smiling more and more. Milly was definitely not like any woman he knew before. Well, she's the first mouse woman he ever met and she was far younger than she appeared, but she was clearly more than that. A part of him worried that it would be wrong to find someone technically so young interesting, but with Animalia, who knows what's considered normal? Still, he wasn't going to do anything stupid until he was sure. Besides, that's no way to treat a lady.