"Not until you have some more." she said smiling. He smiled back and made a little growl noise in his high voice that sounded adorable as he undid the string and held the balloon to his mouth.
He sucked in the helium taking a deep breath.
Almost instantly he felt pressure build right behind his tail bone. He figured it was going to be his new tail. Eagerly, he sucked in more of the balloon's helium and felt the pressure become nearly unbearable to the point John thought he might be physically hurt. PLOP! The pressure lessened as a latex tail popped right out of John. It flopped down under it's own weight before gaining rigidity and rising slowly upward to stick out nearly horizontally.
John held the balloon's nozzle closed. He turned to see his new tail and felt it bob and jiggle. It was the strangest feeling. The tail behaved like a balloon would: it bounced and bopped against his buttocks. He grunted and growled in his high-pitched voice trying to get a good look at the tail.
Carrie giggled, "Here, let me help you." She put a hand on John to stop him turning around and gently took hold of John's inflated rubber fox tail. It was orange at the base and faded to white on the comically large tip. Carrie bent the tail around John's thighs. John shuddered. Carrie's gentle caress send shivers of pleasure though him. John grinned when he saw the tail. It reminded him of playing all those games of Sonic when he'd always play as Tails.
"OK," John squeaked, "I'm a sexy fox and I'm all yours...should I finish this balloon off or should we see what happens when you take a breath?"