In the bizarre world of "Cirque Du Freak: The Vampire's Assistant," there's a war brewing over "portion" control. It seems the truce between those who sip, leaving humans a little weaker but none the wiser, and those who gorge, gluttons who leave death, destruction and no tip behind, has been on hold for a couple hundred years.

But those peaceful days are about to end in "Cirque Du Freak," Paul Weitz's stab at vampire camp, a not-quite-deadly adaptation of the frothy fanged kids book series by Darren Shan. Interestingly, the film's lead character is a 16-year-old named Darren Shan (Chris Massoglia). Coincidence? I think not.

Darren's a good kid, makes good grades and seems to be taking a pass on the whole teen rebellion thing except for his delinquent best friend Steve (Josh Hutcherson). That is, until the Cirque comes to town (cue ominous music). Despite being told not to go, come evening Darren and Steve are there, claiming to be 21. How 16 is that?

There's a good mix of appropriately gross freaks, from the minor -- Snake Boy ( Patrick Fugit), who seems to have nothing more than a bad case of green psoriasis -- to the major -- Corma Limbs ( Jane Krakowski), whose ability to regenerate body parts comes in handy when there's an angry werewolf around. But the real discovery is Crepsley (John C. Reilly) and his performing pet spider, a bright red-and-blue poisonous plush one named Octa.

Darren really likes spiders, and Steve is obsessed with vampires, and he's sure that Crepsley is one. Have they come to the right place or what? Soon there's an Octa heist, a bad spider bite, some DNA testing by a nasty fat man named Mr. Tiny (Michael Cerveris), and Darren's having to make a really major life decision -- like should he become a half-vampire to get the spider-dote for Steve and fool his family into thinking he's dead?

The themes in "Cirque" are typical teenage ones -- feeling like a freak, unsure of who you are or what you want to be in life, ready to fall in love, kinda, especially when the monkey girl (Jessica Carlson) is so cute. This is usually a sweet spot for Weitz, who wrote "About a Boy" with such a lovely blend of sentiment and humor, and "In Good Company," an underrated relationship comedy starring Topher Grace. So it's a disappointment that "Cirque" isn't better.

The film's look has a great eerie Victorian storybook quality to it. The story and characters are mostly sized for the 8- to 10-year-old crowd, but the action -- a lot of rough vampire-versus-vampaneze (the killer vamps) fighting that entails limb tearing, head butting, silver knives and spilled blood -- aims a little older. Meanwhile, the dialogue shoots for something akin to the campy cleverness of "American Werewolf in London" or "Scream."

Weitz can't quite get a handle on what the film should be, despite teaming up with the talented Brian Helgeland ("L.A. Confidential") on the script. Missing here is the multi-level, multi-age storytelling that "Shrek" mastered with sass and that "Up" pulled off in a delightfully old-fashioned way. "Cirque" is harmless fluff, with never enough bite.