Gozer (Symbol)
While Gozer is itself an entity, a demon of terrifying proportions, it is also a symbol for the destruction of the world itself. Gozer takes different forms—as a woman, as the giant Marshmallow Man—but each of these forms stand in for Gozer the destructor, which is itself a symbol of "Judgment Day." The end of the world is at hand and Gozer is the one to bring it about. What is so humorous about the giant Marshmallow Man is not only that it's a giant blown-up version of an advertising mascot (one that Ray loved in childhood), but that it is a lovable mascot that symbolizes the end of the world, complete and utter destruction. The demon represents a kind of massive cataclysmic event that will destroy everything, otherwise known as the apocalypse.
The Church (Motif)
When we first see the Ghostbusters' office at Columbia, before they have even become the Ghostbusters, there is some graffiti on the door from a religious person who thinks that the men's interest in the paranormal is sacrilegious. Indeed, as parapsychologists interested in the occult, the Ghostbusters are engaging in some dangerous, god-less games. Later, when they are brought in to speak with the mayor, a prominent priest comes in to talk to them. This moment is treated comically, as the priest is asked to chime in on the recent outbreak of ghost infestations and says, "I think it's a sign from God, but don't quote me on that." Then, when they watch the Marshmallow Man make its deadly route down the city streets, the Ghostbusters cringe as they see it crush a church. Peter yells, "Nobody steps on a church in my town!" However comically it is presented, the supernatural and paranormal world is put in contrast to the religious.
"Crossing the Stream" (Symbol)
When the men decide to risk it all and "cross the stream," this is a dangerous act of defiance, but their only chance of defeating the evil Gozer. It is also a symbol of the fact that in order to defeat the massive evil that has taken over the city, the men must stick together and pool their resources. As the men pool together their proton streams to dismantle the portal to the demonic realm, the viewer sees that the sum is greater than the parts. No one Ghostbuster is better than the other, and the key to their success is their ability to work as a team to complete their goals. "Crossing the stream" symbolizes the risks they take as well as their potential for success, so long as they work as a team.
The Green Ghost (Motif)
The green ghost, also known as "Slimer," materializes first in the fancy hotel, creating chaos, messing up everything, and drinking all the liquor. Then later, when the storage of all the captured ghosts is turned off, we see him floating out of a hot dog stand in the city and terrorizing New Yorkers. A grotesque green ghost with yellow teeth and crazy eyes, the ghost represents a certain baseness and lowliness, all appetite and mischief. In this way, the green ghost becomes a kind of "id." In psychology, the id is one of three psychic apparatuses, which seeks out pleasure, and follows sexual and aggressive appetites over more refined and elevated interests.
Slime and Goop (Motif)
Throughout, one of the main indications of the presence of ghosts is the slime and goop they leave behind. Because ghosts exist in the paranormal, usually as apparitions rather than substantive concrete entities, the slime and goop become the only markers of their concrete presence in the world. When the Ghostbusters go into the basement of the library, they find large gobs of goop in the card catalog, a piece of evidence which delights Ray. Then later, when Peter chases Slimer through the halls of the hotel, we come to learn from whence Slimer's name comes, when he slimes Peter in a gooey mess. The slime represents the tangible bridge between the alternate undead world and the human world.
