Todd pressed the button, and a lump started to grow at the base of her spine.
Soon the lump appeared to have pushed itself out over the top of her underwear, causing her to momentarily adjust her panties and skirt with one hand. All the while, she remained engrossed in her book, not noticing the change.
The lengthening tail then began to lift the back of her skirt. Todd watched the progress of the hidden tail as it grew under her skirt and smiled. Then, it poked out from the bottom of her skirt.
It was a lion's tail, with a tuft of hair at the end and golden fur running up the length of it. It kept growing until it was a full 3' long.
There she stood with a full-sized lion's tail lifting up the back of her skirt (and revealing her pink panties to anyone who cared to look). She kept reading, oblivious to her change. She even let her tail absent mindedly sway back and forth as she continued to read her book, like it was a perfectly natural part of her body, as if it had been there her whole life.
Todd was ecstatic. His invention worked perfectly. Now, what would he try next?