Continuity mistake: When Dana struggles with the literal arm-chair, one of the arms pops out of the top of the right armrest and a clawed hand clutches Sigourney Weaver's face. Change of camera angle, and not only she is struggling against the demonic limb in a different position, but the hole is gone from the top of the armrest, the arm is sticking from the side. (00:51:45)
Continuity mistake: The lighting in the scene with Venkman stalking Dana outside the concert hall is inconsistent. For instance, when he quips "I've got hundreds of people dying to abuse me", Dana's stiff friend leans against a fountain that is bathed in sunlight. Mere moments later the section of the square is in the shade. (00:43:10)
Continuity mistake: When Venkman radios Ray to tell him about the ghost, look at the cart in the background when Ray answers; the mess does not look the way it looked in the earlier close-up; there's less stuff on the partially knocked down scaffold and the table ricocheted away from the wall but here the flowers are back on it. (00:33:20 - 00:33:45)
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: 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: 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: Egon is done testing Dana with the electrodes on her temples. He walks past her pronouncing a line; " I wouldn't rule out clarvoyance." There's a cut during the sentence, and in the first shot Dana is looking up at him, in the second she is looking at the floor. (00:23:20)
Continuity mistake: When Dr. Venkman investigates Dana's refrigerator, there is a Corning dish and a can of Coke side-by-side on the top shelf. The camera cuts twice, and there is suddenly another item (looks like lunch meat) that appears in front of the Corning dish and the Coke can.