Trivia: Director Ivan Reitman performed the demonic voice of Dana/Zuul in the bedroom scene with Peter Venkman.
Trivia: When Peter Venkman mentions the time Egon Spengler tried to drill a hole in his head, Egon replies, "That would have worked if you hadn't stopped me". This line was ad-libbed by Harold Ramis.
Trivia: Casey Kasem does a voice-over cameo as himself on his radio show after the Ghostbusters become famous. The ditsy blonde woman that Louis dances with at his party is played by Casey's wife, Jean Kasem.
Trivia: The role of Louis Tully was originally written and storyboarded for John Candy.
Trivia: The Ghostbusters Fire House is located at North Moore, & Varick St. in New York, NY.
Trivia: Writer Dan Aykroyd originally wrote the role of Venkman for John Belushi, but approached Murray after Belushi's death. Belushi still appears in the movie (of sorts): the body movement of the Slimer Ghost were based on his movements.
Trivia: Two points in the movie where you can see Staypuft Marshmallows: the first is next to the eggs on Dana's worktop when the eggs start to cook, and the second is when the beam of light is coming out of the Ghostbuster's house, there is a wide shot of it and on the left of the screen there is a billboard advertising Staypuft Marshmallows.
Trivia: The "marshmallow" at the end of the movie is shaving cream.
Trivia: Originally, Gozer was supposed to be a man and the top choices for the character were David Bowie (the decision to get him was made too late to hire a famous actor) and Paul Ruebens (and he was supposed to appear in a business suit).
Trivia: The party scene at Louis Tully's apartment was entirely improvised.
Trivia: Harold Ramis states in the DVD commentary that the "experiment" that Venkman conducts at the beginning of the film is inspired in part by the Milgram Experiment. In the Milgram Experiment, people were told that they would be giving a person increasingly powerful electric shock whenever the person incorrectly answered a question from a list that was read off. (The reality was that the person being "shocked" was an actor and that the generator was fake; the experiment was a test of whether the subject would give a person lethal shocks just because an experimenter was telling them to do so.)
Trivia: After the librarian signs out in the downstairs section of the New York Public Library, she passes the card catalogue shelves which open behind her and suddenly hurl their contents into the air. To achieve this effect, technicians were standing behind the shelves to push them out and then used a copper pipe to blow out the contents.
Trivia: The original title of Ghostbusters was Ghost Smashers.
Trivia: Venkman mentions the time Egon "tried to drill a hole in his head". This is a reference to Trepanation, a procedure alleged to increase psychic abilities among other things.
Trivia: When Peter is in Dana's apartment, she tells him "You're more like a game-show host". This line was improvised by Sigourney Weaver. The original line in the script was "You're more like a used-car salesman."
Trivia: The first time the heroes use their proton weapons (in the hotel sequence), you can see (using slow-motion) that the rays don't actually come from the weapon, but from their target. The rays were "drawn" during post-production and, apparently, it's easier to start drawing from the target to the weapon. (00:31:46)
Trivia: The opening couple of shots were actually shot at New York Public Library. The crew could only film until 10am for one day. All of the scenes in the backroom of the library were filmed at the Los Angeles Public Library.
Trivia: The role of Winston Zeddemore was originally written for Eddie Murphy.
Trivia: The EPA article in the newspaper showing a photo of the ghostbuster is written by "Richard Thornburg". Actor William Atherton, who plays Walter Peck of the EPA in Ghostbusters, would go on to play a journalist named Richard Thornburg in Die Hard.
Answer: Ron Jeremy can be seen in the crowd outside the firehouse right after the containment unit is shut off.