The strange feeling in Dan's body was quickly growing stronger, and he got more worried. "Kat, please!" he begged worriedly. "Don't turn me into an animal! I don't wanna get killed or let out into the wild!"
Kat's eyes widened, and she laughed heartily. "Oh wow, Dan, you're gullible!" For a moment, he breathed a sigh of relief, but then realized the tingling was still building up. "I wouldn't turn you into an animal. I wanna do something... much more interesting," she giggled.
"What the fuck are you talking about?" Dan asked.
"Go look in the mirror," Kat instructed. Dan walked over to it, saw his reflection- and gasped. His face looked very different. His lips were fuller, his eyelashes longer, his cheeks softer, his jawline softer.
"Y-you can't..." he said softly, gasping as his voice softened as his neck and larynx shrunk, and his hair started to lengthen down to his shoulders.
"Oh, but I can," Kat giggled. "It's surprising how malleable human sex is for magical powers. I even tried turning myself into a boy and back again earlier," she commented offhandedly. "You know the weirdest part? It feels really good," she purred, watching Dan's change intently.
Dan didn't want to admit it, but Kat was right- this did feel so good. He felt an intense itch in his chest and pulled off his T shirt just in time to see his nipples perk up and turn more sensitive. The feelings rippled down his hands to his arms and he felt the muscles in them turn more lithe and slim. He panted as boobs formed rapidly on his chest, surprised by how firm and heavy they felt, not to mention how sensitive.
Most of the other changes occurring after that made Dan feel more hazy, his figure curving inwards and his hips flaring outward, his butt swelling and his legs and feet slimming slightly, though all of that made him need to take off his jeans and boxers. When he tried to cover his penis, Kat protested, 'c'mon, I wanna see this, it's the best part!"
Dan wanted to reply 'what the fuck?!', but could only manage "W-wha-" before the changes finally hit his reproductive system. Before his eyes, his erection slowly dulled and his balls moved up inside him, his emptied scrotum slowly tucking inwards and reshaping into a feminine mound. As his shaft continued to shrink, it settled against his skin and slowly formed a clitoral hood while his head became the clitoris itself, while his mound opened out into a sensitive slit. She gasped as she realized her body was completely devoid of anything masculine.
Grinning, Kat came up behind her brother- or rather, her sister- as Danni looked at her new body in astonishment.