Both Chevy Chase and Michael Keaton turned down the role of Dr. Peter Venkman (Bill Murray’s character).

Eddie Murphy and John Candy both turned down main roles.

Eddie Murphy starred in Beverly Hills Cop the same year Ghostbusters was released.

Bill Murray’s role was originally written for John Belushi, but he died while the script was being written.

On set, Dan Aykroyd referred to Slimer as the ghost of John Belushi.

Dan Aykroyd’s script originally took place in the future, but Harold Ramis rewrote it to take place in modern times.

As a result, the production budget was cut from a projected $300 million (according to director Ivan Reitman) to just over $30 million.

The original trailer featured a 1-800 number, not a 555 number, which led to a prerecording of Bill Murray and Dan Aykroyd.

They got 1,000 calls per hour, 24 hours a day, for six weeks.

The Ghostbusters’ firehouse headquarters was remodeled as the mechanic shop in The Mask.

It’s located at 14 N. Moore St., Manhattan, New York.

The marshmallow goo that explodes onto William Atherton is actually 50 pounds of shaving cream.

The Stay-Puft Marshmallow Man suits cost $20,000 each.

Three were made and all were destroyed during filming.

Ray Parker Jr.’s theme song for the film was a No. 1 hit for three weeks.

Huey Lewis later sued Ray Parker Jr. for plagiarism, due to similarities between the Ghostbusters theme song and Lewis’ “I Want a New Drug.”

The jail scene was filmed in a real prison, and Dan Aykroyd was convinced the building was haunted.

Bill Murray only agreed to star in Ghostbusters because they offered to remake The Razor’s Edge with him as the star.

The party scene with Rick Moranis and his guests is almost entirely improvised.

Ghostbusters was the highest-grossing comedy of all time, until the release of Home Alone.

It made $240 million domestically in 1984, which is equal to about $580 million when adjusted for inflation.

The term “proton pack” was never actually used until the middle of Ghostbusters II.

In the sequel, Spengler said “before we go any further I think we should get our proton packs.”

The guns for the proton packs were originally wands.

The wands were changed to laser guns to make it more believable that the Ghostbusters created their gear from practical equipment.

The film was originally titled Ghost Smashers.

But director Ivan Reitman called it “the telephone book” because of how long the first draft was.

Ghostbusters was Larry King’s film debut.

Ron Jeremy was an extra in the film and later starred in a porn parody entitled This Ain’t Ghosbusters XXX.

The cast and crew referred to Slimer as “Onion Head” because of how bad the prop smelled.

To show its massive size, the Stay-Puft Marshmallow Man was originally supposed to come out of the water next to The Statue of Liberty.

But the scene was too difficult to shoot, so they scrapped the idea.

There was a second version of the Librarian Puppet, but it was rejected because it “looked too disgusting.”

It was later used in Fright Night, which was released one year after Ghostbusters.

The demonic voice of Dana/Zuul was performed by director Ivan Reitman.

And most of Bill Murray’s lines were ad-libs.