Katie felt herself growing. Her 13-year teenage body grew to that of x3 its standard size, almost reaching the ceiling of the rusty house. Her already-large breasts grew until they reached the size of G's. Not only did this apply, but she had even grown a 3rd breast between her already-large 2 alongside another pair underneath, totaling to 6 tits. Suddenly, she started growing 2 more arms on each side in conjunction to her breasts. Now, she could not even wear any of her clothing anymore, not even her bra. Her horse body grew with her to a full grown horse body. Suddenly, she look to see her fingernails thicken and become jet-black. She grew an extra 2 elbow ligaments as they all became flexible enough for her to twist her arms as she pleased. In conjunction to her elbow ligaments, her arms grew to x3 their size as well. Next was the top of her head. Her ears had relocated to the top of her head and became pointed, covered in the same fur as her hair, which grew longer in conjunction. Her ears grew and 4 more popped out. Finally, Katie's jet-black hair formed a mane between her ears as it ran down her neck and back, her fur covered her entire body, yet with all this her body still resembled that of an intriguing, seductive woman. The fur that had covered them were lighter than the rest of her body. Her jaw and nose pushed out slightly as the rest of her face grew. Her blue eyeballs augmented themselves to grant her 20/1 vision. Finally, her 4 legs had grown to adjust to the size of her already-large horse body, which had grown to x3 its usual length with 8 extra legs growing out. She felt her horse body become completely flexible, although her legs grew more stiff so she could not twist them. The hooves of her legs adjusted so there was simply 1 giant toe with a flat surface underneath it as if she were wearing a perma-shoe. Her breasts grew so now there were 6 instead of 2, and they became larger as well. Finally, she realized she had grown 3 giant white horns on her forehead resembling unicorn horns. 6 wings grew from her horse body as well as 2 from her back. As soon as her changes stopped she slowly galloped to the mirror to view and admire herself, only to realize she had forgotten her friend in her belly. She felt as if her friend was growing fast within herself when she was consumed by convulsions of labor.
However, Katie felt another kick coming from inside but this time the kick is coming from her horse behind. She looks under her as a large growth starts to grow behind her rump. She had to push her hanging horse breasts to watch through her as the kicking continues and the lump starts to grow until Katie's furry clit splits and 3 spikes appeared, which later appeared to be part of a giant ball that represented Tiff's head.
"Tiff, why are you growing out from my ass?!" Katie screamed.
"I had to find some way out. I tried the way I came in but you've sealed it up." Tiff replied in return. She continued to smudge through via wiggling until her shoulders started to appear. She managed to wiggle out enough for her 2 arms to appear. After pushing out just enough, it seemed as if she looked exactly like Katie. Her hair, 6 arms, 2 wings and 6 breasts appeared to be the exact same as Katie, with no difference at all.
"Tiff, I have just realized you looked exactly like me." Katie noted.
"Doubt, but I still need to get out of here!" Tiff replied angstly. She continued to push through until her legs appeared. It seemed as if she had grew the same legs as Katie, horse-like and huge. Once Tiff tried to look down at her friend's pussy, she realized she had horse legs of her own. Tiff fell on the floor. "WHAT THE HELL JUST HAPPENED TO ME!!!" Tiff cried in horror as she felt herself rising and her back flapping.
Katie wanted to tell her to stop worrying, but she started to feel Tiff pull out of her. Suddenly realizing she could bend her horse-body, she flexed around to grab Tiff and pull her out. Tiff was finally reborn, looking exactly like her "mother"
"WHAT DID YOU DO TO ME!?" Tiff screamed in agony. She flapped her wings angrily, not realizing she was the same size as Katie.
"You decided to tickle my pussy and I still didn't have enough time to train my new body. You also said that you always dreamed of being a centaur, so why aren't you happy?" Katie replied.
"Listen, Katie. I apologize for screaming at you, but if anyone sees what occurs to us, we will become taunted by the entire world for looking like freaks. Imagine if you saw a Unitauress galloping in the streets or flying in the air or what-not. What would you do?"
"I would likely marvel at it, wondering if it were real and praising it."
"Problem is, you don't know if everyone else sees the same thing as you do. Not only that, but that Unitauress could also be an outer-space alien, so you are merely worshipping your near-death".
"So you're calling us space aliens."
"No Katie, but not everyone thinks like you do. We have to fix ourselves or we will never recognize our former lives again."