Two stars of the movie died at an early age in ways which were eerily prophesied by the script: Jeremy Applegate (Peter Dawson, whose character prays he will never commit suicide) committed suicide with a shotgun on 23 March 2000, and Kim Walker (Heather Chandler, who had the line "Did you have a brain tumor for breakfast?") died of a brain tumor on 6 March 2001.
The role of Heather McNamara, the cheerleader, was originally offered to 17-year-old actress Heather Graham. Heather's parents decided against letting her do the role because of the dark subject matter.
Originally, the book that suicidal students supposedly underline "meaningful" passages from was "The Catcher in the Rye". The producers could not get clearance from J.D. Salinger, a notorious copyright stickler, to use this book and it was changed to "Moby Dick" instead, as Herman Melville's works are in the public domain.
Lying on top of the glass table through which Heather Chandler fell were a copy of the Cliff's Notes for "The Bell Jar" (which was written by Sylvia Plath, who committed suicide) and a magazine with a cover story "The Fall of the American Teenager."
The high school is named "Westerburg High". Winona Ryder's favorite band at the time was The Replacements, whose lead singer is named Paul Westerberg. Another reference to the band occurs when J.D. says "Color me impressed", which is the title of a song from The Replacements' album "Hootenanny".
In 2014, a musical theater adaptation of Heathers opened at the off-Broadway theater New World Stages. In a completely unrelated coincidence, the movie had been released by a film production company called New World Pictures. The play is set to appear on Broadway in 2015.
Mid-1990's-era ska/punk band 'Edna's Goldfish' named their song "Veronica Sawyer" after the main character in Heathers. The song's theme of alienation among suburban teenagers reflects the themes of the movie. Reel Big Fish covered the song on their 2009 album "Fame, Fortune and Fornication."
The radio call-in show "Hot Probs" featured in the movie is a version of the now nationally famous KROQ radio show "Loveline", and the radio DJ in the movie is James 'Poorman' Trenton, the creator and original host of "Loveline".
The original screenplay had a different ending in which Veronica kills J.D. by shooting him and then straps the bomb (a much larger and more complicated piece of equipment, described as being "a cylinder as large as a television set") to herself, blowing up as J.D. does in the final ending. What is placed in the final ending as JD's boiler-room speech about "imagine I blew up the school, imagine I blew up all the schools" is contained in a suicide note found in Veronica's locker by Heather McNamara and Betty Finn. The movie ends with an eerie prom sequence set in Heaven, tying into JD's assertion that the only place everyone will truly get along is in Heaven. The prom begins with students dancing within their social cliques, then switching partners in odd pairings like metalheads dancing with Heathers and one of the murdered jocks getting his prom picture taken with a tipped cow; the punch being served is the drain cleaner used in the first murder scene, and "Dumptruck" is singing onstage as the entertainment for the evening. This was intended to be shot but the studio thought it was too dark for the target teenage crowd and opted for a lighter ending.
One alternate ending had Martha Dumptruck stabbing Veronica. Martha shouts "Fuck you, Heather!" Veronica, lying on the ground with a knife in her stomach, replies "My name's not Heather! My name's not Heather!"
Writer Daniel Waters said in an interview: "I did come up with this crazy, cockamamie "Heathers 2" where Veronica becomes a page for a senator named Heather, played by Meryl Streep. The ending is her assassinating the president and getting away with it - and it's a good thing." Winona Ryder has heavily supported the idea for a sequel, but as of 2014, nothing has come out of it.
Winona Ryder claims that she has many favorite moments from the film. The one that usually comes to mind is when she is walking up the hill after seeing JD in the cow-tipping scene. In the background, just barely visible, Heather McNamara is being date raped by one of the jocks. Ryder says the scene is so subversive and dark that once you notice it, you can't stop thinking about it.
The original ending involves Veronica killing herself with JD's bomb, quietly saying "bang" and the school being destroyed. Keeping true on JD's words about how different social types can only get along in heaven. The scene then would cut to black and it would show a prom in heaven with Martha Dunnstock singing to a crowd of different social types dancing together. This was rejected for being too dark.
When J.D. asks Veronica if she takes German, she replies that she doesn't, but instead takes French. He then tells her the bullets they're going to use for their "prank" are German ones called "Ich Lüge" bullets. "Ich lüge" directly translates to "I lie" from German to English.
Winona Ryder claims that this is her favorite movie. She also says that she gets asked about Heathers 2 more than anything else, although a sequel seems unlikely. The filmmakers have suggested that they would like to do the project. One of the plot lines includes JD being a CIA agent before his death. The CIA would then blackmail Veronica and the story would end with Veronica assassinating the President.