All humans have visits from those they knew in the past, now dead. These spirits, who are primarily disincarnate but can come from their next incarnation in an Out-Of-Body, are trying to settle things they feel were left outstanding. These matters can be as simple as an apology they wished to express to you, or a bit of information they felt you needed, intended to be told to you when you next met. Death interrupts the plans. Ghosts are such disincarnate entities. Ghosts often show themselves to humans in a form that the human remembers. This is not a willful act on the part of the ghost, it is the way the humans mind perceives the ghost based on the fact that they understand they are communicating with someone they knew. The mind plays tricks where the human see what he expects to see or hopes to see, and fails to see something they do not wish to see.
This is exactly what occurs when humans are being visited by ghosts. The ghost takes the form that the human recalls, the form the ghost took when they were alive. This form is shaped in the mind of the human as it fits with all the circumstances of the conversation between souls that is taking place. The human has formed this image from memory, but because this memory is swarming about, chemically speaking, with all the other circumstances of the encounter, it merges in the mind of the human. Like scenes that the filmmakers in Hollywood make, where a person on top of a wave may in fact be standing in a room, superimposed on a wave, the human encountering a ghost superimposes what the human used to look like. To the human, this has all been received as one impression.
Not all ghosts are from the dead, as a ghost can be a spirit having an Out-Of-Body experience or a normally disincarnate spirit. The majority of time, during 3rd and 4th Density, an entity will find itself incarnated. Upon death, the entity leaves its physical body, and this can also occur slightly before death too. Many humans experience Out-Of-Body experiences, and these are times when what you call the soul separates from the physical body either because it is curious and wants to go somewhere the physical body cannot, or because the physical body is experiencing trauma. Disincarnate entities are in light form. The reason some such entities appear brighter in light form than others is related to their spiritual maturity. The older and wiser, the brighter. They gain in spiritual bulk, one might say.
When an entity is disincarnate, it can wander about just as the soul can in Out-Of-Body experiences. Likewise, as in Out-Of-Body experiences, it is drawn to places it is either curious about or tied to because of emotional trauma. The entity that feels an issue is unresolved will hang about, desiring to influence proceedings. This is much displayed in your media in ghost stories of one kind or another. Just as with visits from entities in 4th Density or higher densities, these disincarnate entities cannot affect humans unless the human gives The Call. It is not because these disincarnate 3rd Density entities are under the same rules as we, the rules from the Council of Worlds, it is because their substance cannot affect the physical world, and they cannot possess another's body unless The Call has been given and permission granted. In this regard, a walk-in or a possession is a reality, and can happen.
That is hilarious. Spyder's story is truly creepy. 
