Bruce Willis was offered the role as Sam but turned it down because he didn't think the movie would work with the main character being dead most of the movie. When Ghost went on to become a huge success he referred to himself as a "knucklehead" for saying no. Nine years later he said yes to playing another main character who is dead most of the movie - but doesn't know it - in The Sixth Sense (1999), which also went on to become a huge success.
Molly tells Sam that he "leads a charmed life." This is a line from William Shakespeare's Macbeth. Macbeth also claims to lead a charmed life, meaning he cannot be killed. Immediately after making this claim, however, he is killed. Sam is killed after seeing a production of Macbeth.
Bruce Joel Rubin wanted Patrick Swayze to play Sam Wheat after he saw an interview Swayze gave. When he brought up his father, Swayze burst into tears. Rubin thought if a macho guy like Patrick Swayze could cry over a loved one, he'd be perfect for Ghost (1990).
Starting in the early 1990s (shortly after the release of Ghost), hip-hop lyrics often included Patrick Swayze's name or the phrase "I'm Swayze" as a reference to or replacement for the earlier slang, "I'm ghost", meaning "I'm leaving/out of here/gone, etc." The 'Notorious B.I.G.' was one artist who was especially fond of including this phrase in his songs. Swayze's appearance in the video for Ja Rule's "Murder Reigns" was also a reference to the movie's and his own interesting place in hip-hop culture.
The song Sam sings relentlessly to Oda Mae to get her to agree to help him is "Henry the Eighth, I Am". The lyrics, in part, are "She wouldn't have a Willie or a Sam..." Patrick Swayze's character is named Sam, and the man who murdered him is named Willie.
When passing through solid objects, ghosts appear to absorb some of the material they are going through. Jerry Zucker had some difficulty explaining what he wanted this effect to look like. Finally, he illustrated it by dipping a napkin into coffee.
Shortly before production began, Whoopi Goldberg was unsure if she was going to be able to put this movie into her work schedule. The part was then verbally offered to Jackée Harry, who accepted. However, at the last minute, Goldberg was able to do the film after all and Harry was dropped.
Paul Hogan was offered but passed on the role of Sam Wheat because he felt it wasn't funny. However, Paul Hogan offered Patrick Swayze the role of Steve Garner in his supernatural comedy "Almost An Angel", but Swayze turned it down to do this film. Elias Koteas got the part instead.
'Whoopi Goldberg''s character is named Oda Mae Brown. Later in the film, she briefly uses the name Rita Miller. Taken together, the names are a friendly shout-out to writer Rita Mae Brown, author of Rubyfruit Jungle.
The subway scenes were filmed on the abandoned lower level of the 42nd St. station of the IND 8th Ave. line. Trains appearing in the film wrong-railed through the station; that is, they ran in the opposite direction of normal operation.
When they were filming the chase scene at night in New York, it was really cold and everyone else was bundled up except for Patrick Swayze's character Sam Wheat and since he's a ghost they didn't want his breath showing so they made him chew ice. So here's Patrick wearing a flimsy shirt and chewing ice while everyone else is wearing warm clothes.
The trivia item below may give away important plot points.
Luis Guzmán revealed in a documentary focused on character actors that he's frequently stopped by fans of the movie who think he's the actor who played Sam's killer. People ask him why he killed Patrick Swayze to which he always replies that Rick Aviles - the actor in question - was the one who did it.