Ghosts

Ghosts vary from various types of mythical creatures or spirits listed in stories, to a type of paranormal phenomena.

In most cases, it refers to a disembodied soul or spirit of the deceased, though in popular usage, it refers to the physical appearance of a deceased person, although, the usage of Ghost-like activity, has been extended to unexplainable disembodied voices, as well as movement of objects by no known force and random sounds often called "poltergeist" (German for "Noisy Ghost") activity, or in some cases, considered particularly frightening, with unexplainable attacks that leave physical injury, with humans and animals, often called "Demonic" activity.

In the Call of Duty Series, it refers to various in game events, modes of gameplay, or easter eggs put in by the developers.

Call of Duty: Finest Hour
In Call of Duty: Finest Hour, a ghost of a little boy can be seen in the Ghostly Room easter egg.

In the British second level, Depot Sabouteurs, a small house can be accessed, looking similar to a church. Throw to sticky grenades at it, press the Action button. No Icon will appear. Throw one more sticky grenade and when the explosion has cleared you will see a stairway. Go down it to find a strange room.

In the room, there is the ghost of an Arab playing an instrument. He does not acknowledge you are there, just keeps on playing. A Bren LMG can be found, as well as a first aid kit and more sticky grenades. On the walls there are pictures. Some include SAS (Or perhaps PPA) soldiers wearing turbans in a Jeep, and one picture may be of T.E. Lawrence Of Arabia, but this in unconfirmed. The room has a mysterious lighting and a ghostly atmosphere. No one else will follow you down there.

Call of Duty 4: Modern Warfare
Appearing in Call of Duty 4: Modern Warfare, these are usually the cries of children that appear only in places of great destruction. In the level 'Aftermath', when Sgt. Paul Jackson exits the downed helicopter, there is a playground to his upper left. If he were to walk over there he would find that the cries of children can be heard. Some people claim to actually see the ghosts walking around trying to use the things at the playground but it is unknown if there are ghosts there. In the level All Ghillied Up, Lt. Price should be able to hear the same cries of children like before, but it's most likely from being told there were 50,000 people in the town at one point. However, If he were to kill the two men who are dumping bodies into the pond, while they are picking up a body, the programmed AI will still have the bodies get picked up and thrown into the pond, with no one there to do it.

Call of Duty: World at War
In Call of Duty: World at War, there are ghosts in the levels Der Riese, Shi No Numa and Zombie Verruckt. In Verruckt, you can hear disembodied cries and screams. In one room, you can hear a man screaming in agony, and in another room, you can hear a baby and a woman crying. Also, if you turn on the chair in the starting room ( by holding X or square) you can hear a drill and a man screaming afterwards. There's also writing on the walls in the room behind the speed cola. The ghosts cannot be seen, but heard. In Der Riese, the voice of a little girl, with a German accent, is heard through out the level, revealed to be the ghost of Samantha, Dr. Maxis' daughter. Also in Der Riese occasionally, especially when a crawler is made at the end of the round, standing near the power generator near the window a woman's voice can be heard and even voices of children. Same can be heard by the Flogger on Shi No Numa. In all 4 levels of Nazi Zombies (including Nacht Der Otchen with it's demonic laugh), a demonic voice (believed to also be Samantha) is also heard. On Nightfire, many players have claimed to see a ghostly figure of a woman and two men; they have only been reported in private matches with friends. One man has been seen wearing what looks like a Russian uniform and flapcap in the building that resembles a bank and the other near the garage apparently wearing a pilots uniform and leather cap the last is a girl wearing a beret and dark colored clothes and carrying a Sten and seen in the cafe. Some people have a theory that it is Isabelle DuFontaine.