In the 1980s, underground radioactive waste storage projects multiplied, raising the question of "nuclear semiotics." A code or lasting language had to be designed to indicate the danger of these storage sites, which are intended to last for thousands of years. Two scientists then proposed creating a breed of cats that would change color near radioactive substances. Today, against all expectations, the folklore surrounding this far-fetched project might actually be one of the most interesting approaches to addressing the challenges of nuclear semiotics.