Continuity mistake: In the first scene the librarian is pushing a cart of books. In one shot both her hands are gripping the back but in the next shot her left hand is holding the top shelf. (00:00:50)
Continuity mistake: The librarian is carting away books that are (for the greater length of the top shelf at least) leaning away from her. Cut, and they are positioned differently, about one third towards, a part in the middle away, and again towards her. (00:00:50)
Continuity mistake: The shot that introduces the existence of the Ghostbusters is a shot of the door of the "Paranormal Studies" laboratory inside Columbia university. It's a door that opens to the left and bears a glass panel with the names of the 3 scientists. When the shocked kid and Ray use it though, the door swings the opposite way. And when the Ghostbusters get back to their lab and find the Dean there, it's a double door with no glass, which was a prop built just for that opening shot. (00:02:45 - 00:13:10)
Continuity mistake: When Venkman is doing the tests trying to flirt with the blonde student, when she says that the figure on the card is a star, Venkman is first holding the card with his thumb and two fingers. But from the back angle, four fingers are seen extended. (00:03:20)
Continuity mistake: When Peter arrives at the library, the blue book he later slams is on the far left of the table. A frame later it's on the far right. (00:07:00)
Continuity mistake: The large blue book that Peter drops on the table to startle Egon disappears off the table in the next shot. (00:07:10)
Continuity mistake: Venkman is questioning the shocked librarian about possible use of drugs. Director Delacorte in the background is half turned towards them, but he's facing them directly in the close-up when Venkman says "Just asking." (00:08:05)
Continuity mistake: When Venkman walks down to the library's basement, his tie changes from skewed to straight. (00:08:35)
Continuity mistake: When Venkamn picks up slime from the library's drawer, the wood is first partially dry with chunks of slime, but a frame later appears all wet with no slime. (00:09:15)
Continuity mistake: Distance between the guys when they find the ghost librarian decreases significantly between shots. (00:10:40)
Continuity mistake: The future Ghostbusters don't have a clue yet what to do with the ghost of the librarian. They send Peter first, who tries to work his charm saying "Hello. I am Peter." Harold Ramis in the background is pointing the camera at a different height/angle between the two shots. (00:11:30)
Continuity mistake: When the Ghostbusters run out of the library, an old woman in a blue coat is seen on the left side by the bottom of the steps. A second later she is all the way up and coming from the right side instead. (00:12:20)
Continuity mistake: The guys have just been thrown off campus. A liquored-up Peter walks Ray to the right explaining; "I believe that everything happens for a reason." Before the camera cuts away, you can see the head of a girl with a red ribbon in her hair that is going down the stairs. Next shot and she hasn't even set foot on the first step yet. (00:14:45)
Continuity mistake: When Ray first tries the fire pole at the station, he is holding it with his left arm with his right hand on the wrist. When he hits the floor, he is holding the pole with his right arm under his left arm. (00:16:10)
Continuity mistake: When we see Dana for the first time, there is an aerial shot of her taxi pulling over to drop her off. The front end of the taxi drives into the view of a tree, however when Dana gets out of the cab, the tree has vanished and there is a clear view. (00:16:50)
Continuity mistake: When Dana returns to her apartment (the first time we see her do so) she is carrying a bag of groceries. The contents at the top of the grocery bag change with each shot: one time celery, then bread, then eggs, etc. (00:17:00)
Continuity mistake: When the eggs pop out of her bag and start cooking on the counter, they're in different positions depending on whether it's a close up or wide shot. (00:18:55)
Continuity mistake: Dana witnesses the horrific appearance of Zool inside the fridge, and as she tells the Ghostbusters, slammed the refrigerator door shut and left. However, when Peter talks to her in the living room after he checked the fridge himself, you can see that the items on the table (the one by the TV she watched the commercial from) have been radically rearranged, something she surely wouldn't do leaving in a hurry. (00:19:00 - 00:26:55)
Continuity mistake: During the flying eggs scene, the lettuce on the right changes shape and position between angles. (00:19:20)
Continuity mistake: When the eggs are flying in Dana's kitchen, she approaches the counter and comes inches away from it, yet from a wider angle she is several meters away. (00:19:20)
Answer: He places it on the altar just after they believe they have vaporized Gozer with the proton packs. At this point, thinking the ghost to have been destroyed, he sets it down as he believes the job is done and he will not need it.
Jazetopher