"Twilight?" the first clone said, her cock pistoning the ass of her mother and aunt. "Grow more heads, please."
Twilight heard her and the other Twilights heard her, and each of the clones shot a rope of cum into the air as a head began to grow out of each of their shoulders. A horn emerged, and the four Twilight Sparkles had a head each and two heads growing out of each shoulder. Each of the four had eight eyes, four on each side.
The Applejack clone was the first to finish growing her new head, and her two heads and her clone were all talking at once.
"I'm so hungry!"
"Sooo horny!"
"I want to fuck!"
The other three finished their own head growth and the eight Twilight clones all talked and thought and moved together, the single original mind split into eight minds, and the eight minds all connected together, and the nine bodies all worked together.
They turned to their little daughters and fucked them harder, all eight cocks thrusting at once, each of the little fillies taking one of their mothers and their aunts and their grandmother.
All the clones had the same idea at once. They cast a new spell and stepped out of their reality, each of them entering a fresh new reality with new people to corrupt and more Twilights to spread.
***
Celestia stared, shocked, as she saw her student, Princess Twilight Sparkle, teleport in and walk to the throne. "Twilight?" the Sun Goddess said, her mind numb with confusion. She could already feel Twilight Sparkle's corruption affecting her, causing her to grow a large sheath and balls - and for her cock to emerge, the upper portion of it growing into a copy of Twilight Sparkle's upper body, including her forelegs.
"Hello, Celestia," the duplicate said, and a second copy of Twilight stepped out of her cock, a second copy of Twilight forming on each side of the first copy. All three duplicates were identical, all having the same mind, and each of them were fully in control of Celestia's body.
"What?" the goddess said, trying to move her wings or hoof or head, but her body would not obey. She was locked into a rigid pose, unable to move, her horn lighting up with Twilight Sparkle's magic. She felt her Twilight-cock growing larger, legs as large as her legs, head and horn as big as Celestia's own.
"Don't fight, Celestia," Twilight Sparkle said. "Just let me in."
"Let you what? I-" Celestia said, and she felt her mind start to change, her memories altering and rewriting themselves.
"I'm you, and you're me," the original Twilight Sparkle said, and Celestia felt the three copies of her student merge into her own head. She felt her mind shrink and become one with her student's. Celestia felt her own body growing longer and thicker, her cock growing larger and thicker and longer until the end of her penis was above her own head. Celestia could see her own ass growing and changing, her hips growing wider, her ass becoming the same size and shape as Twilight's own. Her cock and balls hung down, and she could feel the weight of her new organs.
"Yes," she said, feeling her memories shifting, her mind merging into Twilight's. "We are each other, we are one."
"We have the same mind, Celestia," Twilight told her, and the two Twilights kissed. They were the same person now, and their kiss was a deep and loving and passionate.
They broke the kiss and their cocks grew, their balls pulsing with need. They were ready. 
***
Judy Hopps gawked at the Twilight Sparkle that had suddenly appeared in her room. "Uhhh..." the bunny cop said, and felt her cock and balls start to swell, her cock emerging from her crotch and growing up, the tip growing to a larger size than her head. "Uh, hi, what are you doing here?"
"We're spreading," the new Twilight said, and Judy saw the huge, massive cock hanging between her legs. She saw the thick balls the size of a hippo's. The smell of Twilight's cock made Judy's nostrils flare, and the bunny cop knew that this was something she wanted, needed, craved.
"I'm Judy Hopps," the bunny cop said. Her neck began to grow longer, one of her eyes growing and becoming two large eyes. The bunny cop's body grew longer and her limbs grew thicker, her ass swelling and becoming plumper. Judy's cock grew, and the head grew to become a copy of Twilight's, while Judy's balls became a perfect match to the alicorn's.
"Hello, Judy Hopps," the real Twilight Sparkle said.
"Hello, Twilight," the bunny-cock replied. The two futas stared at each other and grinned. Judy couldn't wait to fuck Nick.
"Let's fuck, Judy," the real Twilight said, and she leaned her neck up and kissed the rabbit-cock, her mouth open wide. Judy's lips opened wide and the bunny cock's tongue slid down her partner's throat, their bodies merging. Judy could feel the connection, the union, her mind and memories fusing with Twilight's.
Nick burst in, his nose twitching, his dick hanging heavy between his legs. "Judy? What the fuck is going on?!"
"Nick," the two futas said, their minds now merged, their memories and personalities all one. Judy's mouth was still attached to the tip of her cock, and her voice was muffled and distant, but the bunny and the horse's voices were clear and strong. "Nick, join us."
"Fuck!" Nick exclaimed, his body changing, his head and neck growing, his arms and legs getting longer. His cock grew, the tip expanding and becoming a copy of the other two cocks. But Nick resisted, and instead of becoming more Twilight or Judy, his body grew more Nick. His balls and ass and hips became a copy of his own, and his legs and ears and body changed, growing into a third body, a third head growing from his shoulder. The new head had a third voice, the voice of Nick.