During filming, Laura Dern passed out when David Lynch asked her to smoke four cigarettes at once in one deep inhalation. When she came to, she saw a worried Lynch standing above her asking: "Tidbit! Are you alright?"
Willem Dafoe is actually urinating in the toilet when he goes to visit Laura Dern and asks to "piss in your head". Apparently, Dafoe had drunk a lot of bottled water and really needed to go. Only later did he find out that the toilet was not a working one and some poor crew member had to clean it.
Sherilyn Fenn's accident scene came from David Lynch's impression of Fenn as a porcelain doll, and from the idea of seeing a porcelain doll breaking. He kept telling her about that, and that's how the scene was born. Lynch said of the scene, "I just pictured her being able to do this. She's like a broken china doll". Lynch got the same inspiration for the car accident scene in Mulholland Drive (2001). His direction to actress Laura Harring was to act like a broken porcelain doll.
The snakeskin jacket Sailor wears in the film was actually Nicolas Cage's own. Cage asked director David Lynch if he could wear the jacket in the film, as a tribute to Marlon Brando's role in The Fugitive Kind (1960). After filming was completed, Cage gave his jacket to Laura Dern. (On a side note, "The Fugitive Kind" was based on the play, "Orpheus Descending," by Diane Ladd's cousin, Tennessee Williams. Laura Dern's parents, Diane Ladd and Bruce Dern, met while appearing in a 1961 stage production of "Orpheus Descending.")
Before filming started, Laura Dern and Nic Cage went on a road trip to Las Vegas in order to bond and get a handle on their characters. It was Dern's idea with her stating, "We agreed Sailor and Lula had to be one person, one character, and we would share it".
The film was completed one day before it debuted at the 1990 Cannes Film Festival in the 2,400-seat Grand Auditorium. After the screening, it received "wild cheering" from the audience. When Jury President Bernardo Bertolucci announced Wild at Heart as the Palme d'Or winner at the awards ceremony, the boos almost drowned out the cheers with film critic Roger Ebert leading the vocal detractors. Barry Gifford remembers that there was a prevailing mood that the media was hoping Lynch would fail.
The MPAA told Lynch that the version of Wild at Heart screened at Cannes would receive an X rating in North America unless cuts were made, as the NC-17 was not in effect in 1990, at the time of the film's release. The director was contractually obligated to deliver an R-rated film. He made one change in the scene where a character shoots his own head off with a shotgun. Gun smoke was added to tone down the blood and hide the removal of the character's head from his body. Foreign prints were not affected. The Region 1 DVD and Blu-rays contain the toned-down version of the shotgun scene.
Not counting Twin Peaks, this is the only one of David Lynch's films to have a sequel - 1997's Perdita Durango, directed by Álex De la Iglesia and starring Rosie Perez as the titular anti-heroine, originally played by Isabella Rossellini.
Lynch was originally going to produce, but after reading Gifford's book decided to also write and direct the film. He did not like the ending of the novel and decided to change it in order to fit his vision of the main characters.
The band "The Vandals" used the quote from the movie: "This jacket represent a symbol of my individuality and my belief in personal freedom" in their song "I don't wanna change my pants", only with "jacket" replaced by "pants"
Two distinct references to American thrash metal are made in the film: first, the band that plays in the club where Sailor and Lula go dancing is Powermad, who were from Minneapolis. The 2nd occurs very late in the film when a gang member wears a Metallica shirt.
The trivia item below may give away important plot points.
Originally after Johnnie is killed by Juanna and her henchman, there was a sex scene involving Juanna and Reggie. Test audiences found the scene to be too disturbing and 50% of the audience walked out.