The challenge is here. This is something I had lying around that I wrote originally in March 2009. Maybe I'll post the whole 650-word version tomorrow.
The bouncy ball was bisphenol-b. When the princess accidentally tossed it into a well, it sank to the bottom.
A frog croaked, "I'll fetch it for you, for a kiss."
"Okay," the princess said.
"Kiss, then ball," the frog said.
Their lips touched. The frog grew and the green localized to tights and a jacket; obviously a prince. The princess forgot about the ball.
They didn't live happily ever after. As a frog, the prince had absorbed a lot of pseudo-estrogens. His vestigial third leg gave the princess the willies, and his sperm count was insufficient to provide heirs, anyway.