This is an entire section in zohar and kabalah in general. This concept of what we are calling here ghosts are real and do happen and exist. No joke. Whether or not we understand exactly what is being talked about could be under question. In other words do we fully comprehend who what where when why and how such things happen? Possibly not but they definitely happen and exist. Now we may also not fully comprehend the situation when it happens to be able to know whether or not what is happening is real as the mind is a very complex tool.
Zuberman