At times, Jennifer’s Body is like Heathers (1989) re-imagined as a horror film with Fox in the nihilistic Christian Slater role and a dash of Idle Hands (1999) thrown in for good measure. Both films feature a series of teen deaths and show how the media exploits them while a shell-shocked student body tries to cope. Both films also feature pitch black humor with Jennifer’s Body gleefully skewering popular culture.
Cody’s screenplay is smart and witty but the overabundance of pop culture references does instantly date it, which I’m sure will be part of its appeal to the cult following that will no doubt form once all the hype goes away. As she demonstrated with Juno, Cody has an uncanny knack for authentically capturing not just how teenagers speak but act as well. This is especially true of teenage girls and she does a good job depicting the relationship between Jennifer and Needy. Before her transformation, Jennifer wielded all the power while Needy worshipped her, but when Needy realizes what her best friend has become, she takes on a more assertive role, acquiring her own power.
On the extended version, Kusama returns to do a commentary on her on. Thankfully, it jumps to specific moments in this version that differ from the theatrical one. Kusama says that this version more accurately reflects Cody’s original script. She explains why this footage has been put back in and, in some cases, why it was not in the theatrical version.
I also recommend checking out a really great take on the film over at the Final Girl blog and also a fantastic analysis over at John Kenneth Muir's Reflections on Film/TV.