You’ve probably seen pictures on the news of Lancelot Encore, an endearing Golden Lab puppy that was cloned using frozen DNA from his deceased predecessor, Sir Lancelot. Sir Lancelot’s Florida family paid $150,000 to a South Korean pet-cloning company to re-create him in the form of a fluffy new puppy.

What is not reflected in the happy photos of the new puppy are the mistakes that might have come before him. Cloning mammals, especially dogs, is difficult. Scientists have to create and implant many embryos to birth a healthy one. (During the cloning process, DNA from the adult donor must be reprogrammed back to its embryonic state; that process can sometimes, perhaps most of the time, be incomplete.) RNL Bio, the commercial pet-cloning company, hasn’t given a lot of details on the cloning process or posted figures on the number of embryos that it took to generate Lancelot Encore. But according to an article by the BBC, the success rate using the current method is in the single digits. In a recent experiment testing a new approach, two puppies were born from 84 embryos implanted into five surrogate mothers.

What of the other 90 percent? Some of those likely fail to implant, or spontaneously abort early on, but some may survive much longer and be stricken with serious or fatal health issues perinatally. I asked Robert Lanza, cloner extraordinaire and chief scientific officer at Advanced Cell Technology, about the downsides of cloning. (Lanza has cloned several endangered animal species, both successfully and unsuccessfully.)

Anyone who wants to have their pet cloned should ask themselves if they are willing to have one or two defective copies of “Fluffy” or “Spot” put down in order to get their pet back. Of course, cloning is associated with lots of abnormalities and genetic defects–and a significant percent of newborn animals die in the first few days or weeks of life.

Anyone who thinks they might be able to get Spot or Fluffy back is mistaken. Cloned animals have distinct personalities, just like identical twins. We cloned a herd of cattle several years ago–they were all cloned from a single individual. Yet they developed a social-dominance hierarchy just like a herd of ordinary dairy cows. The cloned animals exhibit the full spectrum of behavioral traits, from curious and inquisitive to timid and shy. There’s no doubt about it: each cloned animal has its own unique, individual personality.

Note: The situation described above is distinct from human therapeutic cloning. The purpose of the former is to create an animal, while the purpose of the latter is to create stem cells for therapies or research. In human therapeutic cloning, which has yet to be accomplished, scientists would remove stem-cell precursors from the embryo early on, and embryos would never be implanted or allowed to develop past that early stage.