Doane Gregory
Megan Fox, left, Amanda Seyfried star in the horror movie "Jennifer's Body."

JENNIFER'S BODY — ★1/2 — Megan Fox, Amanda Seyfried, Johnny Simmons; rated R (gore, profanity, violence, vulgarity, sex, slurs, brief drugs, brief nudity); in general release

The expected various organs and parts in "Jennifer's Body" include a mouth.

That turns out to be an unfortunate thing, because the title character is played by alleged actress Megan Fox, who sounds utterly ridiculous and is unconvincing spouting the hipster-ish dialogue featured in this gory horror-comedy.

As for the film, it tries to be equal parts snark and snarl — think "Mean Girls" meets "Carrie." But it's unsuccessful at doing either of those things well.

While "Transformers" star Fox is top-billed, Amanda Seyfried ("Mamma Mia!") gets most of the screen time. She plays Anita "Needy" Lesnicky, the best friend of the title character, Jennifer Check.

They've been pals since childhood. And they've gotten even closer since they survived a fiery club accident that killed most of the other patrons.

Still, their relationship becomes strained when their high-school classmates turn up dead, and there's evidence to suggest that Jennifer is doing the killing.

But Needy can't convince anyone that's the case — not even her own boyfriend, Chip (Johnny Simmons). He might want to, though, because he's apparently going to be the next victim.

You'd swear that screenwriter Diablo Cody must have been watching a lot of "Buffy the Vampire Slayer" when she wrote this script. (Allegedly, it was written around the same time she crafted her Oscar-nominated "Juno" script.)

But she's sabotaged by Fox and director Karyn Kusama ("Aeon Flux"), who apparently told the stars to remain detached and aloof. That's even true of the normally warm Seyfried.

And neither Kusama nor Cody can find anything substantive for the talented J.K. Simmons, Cynthia Stevenson and Amy Sedaris to do.

About the only person who escapes unscathed is Adam Brody, who's amusing as the leader of a sinister indie-rock band.

"Jennifer's Body" is rated R and features graphic gory imagery, strong sexual language (profanity, slang and other graphic talk), strong violent content (creature attacks, stabbings, explosive and fiery mayhem, vehicular mayhem, and violence against women), simulated sex and other sexual contact, derogatory language and slurs (some based on sexual orientation), brief drug content and references (anti-depression medications and laxatives), and brief watery nudity (as well as a nude anatomical display). Running time: 102 minutes.