To prepare for her role as a possessed living-dead teenager, Megan Fox lost around 15 lbs, bringing her weight down to a near-frail 97 lbs, and stayed out of the sun.

The "waterfall that goes nowhere" is the Devil's Kettle, at Judge Magney State Park in Minnesota. The water disappears into a glacial pothole.

Jennifer and Needy were originally going to have a sex scene in the film.

In a February 2016 interview with The New York Times, while trying to illustrate how completely the studio's (all-male) marketing department misunderstood the point of this movie, director Karyn Kusama recalled that one of their marketing ideas was for Megan Fox to do live chats with amateur porn sites. Kusama said that she begged them to not even mention the idea to Fox because "she will become so dispirited....It was crushing."

The name 'Needy' Lesnicky comes from writer Diablo Cody's initial intention to have the character be of a 'needy' disposition. She later decided against this as she felt she had seen enough nerdy stereotypes in high school set movies.

Despite mixed critical reception, the film has gained a strong cult following over the years. It even garnered an unofficial musical in 2018.

The title is from the song "Jennifer's Body" by Courtney Love's band Hole.

Blake Lively turned down the role of Jennifer, due to scheduling conflicts with Gossip Girl (2007). Megan Fox was later cast.

Diablo Cody wrote the screenplay for the film in 2006, the same year she wrote Juno (2007).

The director's cut of the film was removed from Australian supermarkets due to the graphic sex scene and the violence.

The demon who possesses Jennifer Check (Megan Fox's character) closely resembles a succubus (plural succubi), from Jewish, Christian, and Sumerian mythology/theology. It is said that succubi seduce men, and fornicate with them until they are "drained" (in the movie, getting "drained" could mean getting drained of blood instead of semen). Some possible examples of succubi are Lilitu (from Sumerian mythology), Lilin, and Lilith (both from Jewish theology).

The filmmakers considered actual rock stars like Pete Wentz and Joel Madden for the role of musician Nikolai. The role eventually went to Adam Brody.

Amanda Seyfried auditioned for the role of Mikaela in Transformers (2007). The role went to Seyfried's costar Megan Fox.

Jennifer's surname 'Check' was initially intended only to be a place holder name. It comes from writer Diablo Cody using the phrase 'check' to express the filling of the various required roles, e.g "Jennifer - check, Needy - check" and so on. The name was never changed and features in the final film.

Megan Fox (Jennifer) and Amanda Seyfried (Needy) have both said this is their favorite movie of their respective filmographies.

There was no makeout scene between Needy and Jennifer in the original script.

The screenplay for this film was featured in the 2007 Blacklist; a list of the "most liked" unmade scripts of the year.

Hershey's chocolate syrup was used for Jennifer's 'black vomit' scene along with the use of CGI-animation.

The first poster was unveiled in July 2008, at the San Diego Comic-Con. It showed Jennifer licking a drop of blood from her lips.

Colin invites Jennifer to "Rocky Horror at the Bijou," a reference to a student-run movie theater at the University of Iowa. Diablo Cody graduated from the University of Iowa.

The band's name in the film was originally "Soft Shoulder" before being changed to "Low Shoulder."

A few actors from Diablo Cody's Juno (2007) appear in Jennifer's Body (2009). J.K. Simmons, Valerie Tian and Aman Johal. The film is also co-produced by Juno (2007) director Jason Reitman.

In Diablo Cody's previous film, Juno (2007), fitness personality Tony Little is mentioned. In this film, a clip of Little's show is featured.

Amanda Seyfried and Kyle Gallner both previously appeared together in Veronica Mars (2004). A high school drama involving murder.

When Needy tells Low Shoulder that her best friend is a virgin, and she tells Jennifer ,who retorts to needy "I'm not even an anal virgin!" Was changed for later viewings to "I'm not even a backdoor virgin!"

Low Shoulder was the fictional name given to the band in the movie. In real life, the band was known as No Country. They were called No Country from 2009 until 2014 when they changed their name to Wildling. Prior to No Country, the band had been known as Test Your Reflex from 2004 until 2009. Lead singer, Ryan Levine wrote much of the original music heard in the movie.

A draft of the script was leaked online in early 2008.

Promotional material for the movie was released up to 15 months before the release date.

The studio wanted to promote the film by having Megan Fox do a live video chat on a porn website. Director Karyn Kusama was outraged and horrified by this suggestion. She refused to allow them to do this and didn't even tell Megan Fox about it because she didn't want to dishearten her.

For the scene where Jennifer is swimming naked in the lake, Megan Fox wore a flesh colored bikini.

Feature film debut of Megan Charpentier.

The two pinball machines in the bar are both Williams' machines. Fire! (1987) and The Getaway: High Speed II (1992)

Jennifer is a cheerleader. Megan Fox was a cheerleader at high school.

Diablo Cody: In the Melody Lane sequence. At first, you just see her holding a drink but later, when Jennifer says she'll score some alcohol by "playing Hello Titty with the bartender", the bartender who serves her turns out to be Cody.

Lance Henriksen: The driver who picks up a hitchhiker at the end.

this movie shares some similar plot points with the movie Ginger Snaps, both movies involve two female characters that are close at first, but become enemies, Both movies involve one of the characters being attacked at night in the woods but surviving and becoming evil. Both movies involve the evil character becoming rude to the good one. In both movies the character turned evil starts killing boys from school and eating them. In both movies the good character finds a way to kill the evil one searching in the School's library. In both movies the love interest of the good character is bitten and killed by the evil character, and both movies end around a school party as well as ending with the good character stabbing the evil one in the heart in their own home. At the end of both movies the good character is bitten and becomes evil as well.

In the scene where Jennifer seduces Needy (before they kiss), Jennifer is wearing an "Evil Dead" t-shirt. Plus there is an "Evil Dead" poster on the wall of the bedroom which is center screen for part of the scene. Both movies have an evil force in the woods, that take possession of a young female, and that preys on school friends.

When the car that picks Needy up begins to drive off , the highway advisory sign is the one for "low shoulder"

A Fall Out Boy poster is shown above Jennifer's bed before Needy enters the room to kill her.