One can't help comparing Juno and Jennifer's Body in any assessment of either movie; they're too similar not to. And so, if there's anything that we can learn about Diablo Cody from her writing style, it's that: She likes Hole (interpret that how you will), she has a strange fascination with Tony Little's Gazelle, and she is something of an unofficial spokesperson for Benihana.
When Jennifer's Body first came out in the theater, I was hesitant to see it, mainly because Diablo Cody has bristled my feathers by sashaying into the Hollywood elite without really trying, which is simply how the universe functions. Before I could swallow my pride and put aside my issues (As Jennifer would say, "You're totally Jell-o, you're lime green Jell-o and you can't even admit it to yourself"), the movie had vanished from the theater, peaking at number five at the box office.
Much to my surprise, however, I found myself liking it much better than Juno once I finally saw it. The ridiculous dialogue seems to work better in this movie than it does in Cody's Oscar winning debut. One example is when Jennifer's best friend Needy (Amanda Seyfreid) asks her boyfriend Chip (Johnny Simmons), "Who's Phil Collins?" and Chip reservedly responds, "Forget it. He's seminal, but whatever." And from the moment Jennifer experiences demonic transference, there is a no holds barred outlook on aberrant lines (like when Adam Brody as Nikolai, lead singer of the band Low Shoulder, explains to Jennifer that he has to sacrifice her to Satan by saying, "Do you know how hard it is to make it as an indie band these days? There's so many of us and we're all so cute and it's like if you don't get on Letterman or some retarded soundtrack, you're screwed.") and general profligacy.
Jennifer's Body actually has quite a bit more going for it than Juno, and not just Adam Brody, who always plays an asshole so well. I think what prevented Jennifer's Body from having the same success as Juno is the expectations that were put on Cody's follow-up to such a critically acclaimed film and the fact that many audiences had a difficult time deciphering the tone of a movie that features both Megan Fox eating the innards of a boy in her English class and Amy Sedaris as a deadbeat mom (making a brief cameo in a role that is as close to Jerri Blank as you'll ever get).
The main flaw, it seems, is that Cody is afraid to totally break away from doing the same thing: Jason Reitman is still her partner in crime, certain pop culture references are recycled (as mentioned above), Valerie Tian reappears as a correspondingly high-strung comic relief character (she played Su-Chin in Juno), and her main characters share one uniform voice--Cody's.
With upcoming projects like Sweet Valley High and Breathers: A Zombie's Lament, it looks as though Diablo Cody might be able to make something of this melding of the teen/zombie/horror genre, if she would only just let go of the tone responsible for her success, Juno.