In an effort to seek out new sources of healthy donor organs for humans, scientists at University of California, Davis, successfully injected human stem cells into pig embryos using the gene-editing system known as Crispr, the Guardian reports.
They're not trying to create an army of mutant pig people like real-life versions of Bebop and Rocksteady, though. Had the scientists not terminated their hybrid experiment after 28 days, they believe that the pig would have developed normally, but grown a healthy human pancreas internally.
"You are basically creating a vacuum—a hole—so that the human cells respond to the right cues, they make a pancreas. The pig cells can't," Francis Crick Institute geneticist Robin Lovell-Badge explained to the Guardian.
While it's certainly a significant scientific leap, some critics are concerned a transplant from a different species could spread animal viruses to humans. Others worry mixing DNA across species could affect the animal's brain, conceivably giving birth to a Pigman capable of breaking out of a mental hospital and stealing George Costanza's car like in that episode of Seinfeld.
But Professor Pablo Ross, head of this whole pig embryo experiment, said the potential for the pig to develop a human brain is actually "very low," so don't worry about it.