The Bonsai Kitten web site is a joke, not an actual promotion for the making of bonsai kittens. Investigations by law enforcement agencies, including the FBI, have already determined no real cats were harmed in the creation of the pictures used on the Bonsai Kitten web site. Signing a petition to shut down the Bonsai Kitten web site will not prevent any kittens from being harmed, because no kittens were harmed in the first place.
It was all a joke, one which some say was in terribly poor taste. If that was your reaction, take comfort in the knowledge that many others thought the same.
How could you have known the Bonsai Kitten site was a satire despite its lack of "This is a joke!" banners emblazoned across it? Satire doesn't always announce itself as such (some feel that would ruin its humor), so in cases like this, one dusts off the common sense and aims it at the problem:
The process described is impossible: animals so treated would die long before they could be "molded."
The web site offers no way to purchase the materials advertised. A real commercial enterprise wouldn't build consumer interest through a flashy web site then fail to offer anything for sale. (The site does include a page of "Helpful Tools & Supplies" but provides no form through which they can be ordered.)
The "Bonsai Kitten" site displays no actual pictures of the finished product. There are plenty of pictures of kittens in jars which can comfortably accommodate them (cats are quite elastic and can fit into very small spaces without discomfort), but there are no photographs of molded kittens on display.