They fall from the Path. The basic nature of a buddha has no such form. Keep this in mind, even if something unusual should appear. Also at the appearance of spirits, demons, or divine beings, conceive neither respect nor fear. Your mind is basically empty.
All appearances are illusions.
Don't hold on to appearances. If you envision a buddha, a dharma, or a bodhisattva and conceive respect for them, you relegate yourself to the realm of mortals. Devils and demons possess the power of manifestation. They can create the appearance of bodhisattvas in all sorts of guises. But they're false.