The USA Today cover, dated Oct. 8, 1984 lists an obituary for The Thin Man actor William Powell, who actually died on March 5, 1984. The designer of the faux covers, Mike McWillie, probably used the actual March 6th USA Today cover as the basis for his mock-up. (The text on the cover is only readable on the high-definition Blu-Ray version of the film.)
Ray declares the phenomena they are witnessing may be as important an event as "the Tunguska blast of 1909" in Siberian Russia. This occurred on June 30, 1908, not 1909. (It should be noted that when combined with his misquote of Revelations (see below), many fans consider this to be a quirk of Ray's; that he sometimes gets his facts just a little bit wrong.)
Venkman tells Egon he has Dana "whacked up with 300cc" of Thorazine, a relaxant and anti-psychotic. "300 milligrams" would be more correct, as proper and vital practice is to describe dosage by weight, not volume. Besides, "300cc" is almost one-third of a liter of solution, certainly not doable given the circumstances but certainly fatal to Dana had it been so, if not diluted with sterile saline down from the standard 25mg/cc vials. That being said, 300mg Thorazine all at a single administration is exceedingly high even for severely disturbed patients. While it is likely an error, it could mean that a 300cc dose is necessary given the vague nature of demonic possession.
Near the beginning of the film Venkman is conducting an experiment, in which he says he is using Negative Reinforcement. Two test subjects guess the symbol on the back of the card. Venkman administers electric shock for wrong answers, and gives praise for correct answers. (Of course, he's cheating, but on with the content critique.) Psychologically and Scientifically speaking, Negative Reinforcement is the subtraction of a variable in order to reinforce/increase the frequency of a desired behavior. Venkman is actually engaging in Positive Punishment, the addition of a variable/stimulus (in this case the electric shock) designed to decrease the frequency of a behavior (wrong answers). In Behavioral Psychology, Negative and Positive do not refer to traditional ideas of good or bad but rather the addition or subtraction of a variable in order to enhance or discourage a given behavior.
In the scenes where the gang is about to enter Dana's building, an over-enthusiastic extra with ginger hair in an '80s cut can be seen in two different crowds that are supposed to be facing each other.
During the "montage" there is a shot of the guys carrying their loaded traps out of a building and crossing the street. Just before the next clip comes in, the shot reverses and runs backwards for a few frames.
When Dana gets out of the cab her groceries include a green leafy vegetable with a large white stem but when she gets to the hall it has become completely green lettuce. It changes to celery while she is talking to Louis. When she sets it on the counter it is still celery but in the next shot the item on the counter is lettuce. After the eggs start frying on the countertop it changes to lettuce and celery each pointing in opposite directions. When Venkman is checking out the apartment they are both pointing the same direction.
In the birds-eye view of the Ghostbusters walking through the wreckage of the penthouse, there is still sunlight bouncing off the building despite the fact that New York is supposed to be covered by a big black cloud.
When we first see Alice the librarian, the books on the top shelf of her cart are all set spine-up, leaning back towards her. When the shot cuts to a wider angle, there's now a short stack in the middle of the shelf, with books on either side leaning against it.
When the "marshmallow cream" falls from the top of the building onto Walter Peck, the splash is large enough to cover the rear driver's side corner of the Ecto-1. During the end credits, when the Ecto-1 is driving away, the same rear driver's side corner is clear of "marshmallow cream."
When Peter, Ray and Egon come out of the library, Egon's hair is noticeably different than it was while they were inside. When they go into their office to find they've been fired, it's back to how it was before.
When Venkman comes out of the crumbled street, he has a small circular bandage on his right temple near the hairline, possibly an injury from a previous take. The next time we are able to see him from that angle is on the apartment building rooftop, and the bandage is missing.
When the Marshmallow Man is walking down the street (seen from the Ghost Busters' perspective, before the tiny hydrant explodes) the cables used to maneuver the character's face can be seen by his right foot.
The Dana's building is located at Central Park, Manhattan. The police car in front of the building is from the 41st Precinct, which is located in the South Bronx on Simpson Street. This car would not be in that area.
After the containment unit is shut down, Peck says that the Ghosbusters are 'in criminal violation of the Environmental Protection Act'. However, there is no such act, law, or guideline. There is a National Environmental Policy Act (NEPA), Clean Water Act (CWA), Clean Air Act (CAA), and many other environmental policies; The Environmental Protection Act is not one of them. Also, it is normal for a STATE agency representative to deal with any potential violations before requesting assistance from the EPA- the EPA could not possibly check up on every new potential hazardous business in the Region.
The Hittites/Babylonians/Sumerians are said, by Venkman, to have worshiped Gozer around 6000 BC. The Sumerians come into history around 4000 BC, although they could have existed for some time before then. The first Babylonian empire in Mesopotamia was from 1900 to 1600 BC, and the second one was from 626 to 539 BC. The Hittite empire was from 1600 to 717 BC. Considering that Gozer is a fictional god invented solely for this movie, and that the referenced civilizations all existed in the same general region, and the later civilizations' religions were influenced by those of the earlier civilizations, there is no reason that there couldn't be, in the context of this movie, a Gozer cult in the Hittite culture.
In the scene in Dana's apartment where Venkman is examining the contents of the refrigerator, a can of soda on the top shelf appears to switch between Coke and Coca-cola several times. However, there are two cans in the refrigerator - one says "Coke" and the other says "Coca-Cola".
Dr. Peter Venkman claims that he has doctorates in psychology and parapsychology. Later in the movie, he says that he sedated Dana Barrett/Zuul with Thorazine. Doctors of psychology, or parapsychology for that matter, are not MD's and so are not authorized to prescribe or administer drugs, especially a controlled substance such as Thorazine. However, someone as clearly immoral as Venkman would do so regardless of his credentials.
The Ecto-1 has blue lights but only a government vehicle like police, fire, or ambulance would be allowed to use blue flashing lights on a vehicle. The State of New York only uses Red lights for emergency vehicles. Blue lights are never used on government vehicles.
When Winston and Ray are in the car talking about the Bible verse, Winston is in the driver's seat. When they pull up to the HQ after the explosion, Ray gets out of the driver's seat. (They may have stopped and switched seats between the scenes.)
In the scene when Ray and Winston are in the Ghostbusters car driving over the New York bridge, Winston is at first wearing his Ghostbusters uniform. When we see them exit the car after arriving at HQ, Winston is wearing a checkered shirt. There is a significant time gap and since the uniform is one piece, it is possible that Winston took it off when they stopped somewhere (see above goof).
When Dana enters her apartment after Louis cajoles her to bring her date to his party (and locks himself out again), her obviously touch tone phone rings like an old rotary. However in the 1980s touch tone phones existed that had an actual bell in them and could emulate the tone of an old rotary phone.
Based on editing and dialogue, Ray buys the Ecto-1 car earlier the same day as the Sedgewick job. Given Ray's list of repairs the car needs and its initial appearance, it would take more than one day to get Ecto-1 to the painted-and-equipped state seen at the Sedgewick that night.
The scene where Venkman meets Dana after her recital and arranges their date is cut between two scenes where Winston is instantly employed and hurriedly trained. In the other two scenes, all characters are wearing the same clothes, implying they occurred at the same time. However, Venkman is present in all three scenes and could not travel between the two locations in such a short amount of time. Also, during the scene with Dana, his uniform is clean, and he's wearing an orange shirt.
During the scene where the Ghost Busters are about to enter the building and the ground begins to break apart, you can see that the pieces of ground are not all solid. What appears to be a brown colored sheet billows out as one piece slopes down.
When we first see Dana Barrett (getting out of a taxi), there is a shot of the avenue below her apartment from the roof, just before she steps out of the cab. On the side of the roof there is the head of a gargoyle with protruding sharp teeth - and "through" the teeth we can see the yellow traffic lines separating the lanes on the avenue below, showing the compositing used to achieve the shot.
The goof items below may give away important plot points.
Prior to the final battle, the sky clouds over and darkens when the Ghostbusters prepare to enter Dana's building. Following the explosion, the sky clears to reveal stars. As they exit the building, it's sunny again.
The photo of the Ghostbusters in the newspaper under the "Chinatown Spook" headline during the montage is clearly lifted from the "cross the streams" sequence later in the movie. (Compare the poses, positions and expressions.)