This is when a person or animal or thing auto-invisible-izes, i.e. makes itself invisible. Devil-Cat knows how to do this very effectively. When Mr. Rosebank was young, he made a detailed study on it but unfortunately the report somehow went into Invisibility Mode itself. He searched high and low (and medium) for it, unsuccessfully. This is what prompted him to invent his now-famous Anti-Invisibility-Goggles. But it was too late. The goggles took a year to develop and the report was never found. It is believed the school cleaning crew threw it into the trash by mistake. So sadly we can’t tell you anything about how Invisibility Mode actually works. Sorry!