Ginger Snaps (2000)

Somebody has violently decimated a golden retriever. The opening is shot like a slasher film. The neighborhood is experiencing "wild animal" issues.

The neighbors are two depressed goth sisters who are idly planning their suicides, but can't decide how to maximize the coolness factor. The redhead (shockingly named Ginger) is more into the suicide pact than the brunette (Brigitte), but they're both game. They test out all of the ways to die with costumes and props to get a feel for the possibilities, and submit the resulting film as a school project.

The boys at school are all newly interested in Ginger, who is actively getting her first period, which seems to attract them like dogs. The girls go out for a night walk while she's menstruating down her leg, and the "wild animal" shows up and drags Ginger into the lame suburban excuse for woods. A rubber werewolf bites her a lot while the camera swirls around wildly to lessen our focus on the cheap costume.

The cameraman, forgetting his job, zooms right in on the cheap costume right as the werewolf is hit by a delivery van and explodes into a mist of cherry-red blood. When asked what he hit, the kid who was driving sarcastically says "it looked like a lycanthrope to me."

Ginger is badly wounded, but her wounds speed-heal before they can fetch any adults. It cuts to a video about viral infection of cells in their biology class, and Ginger looking miserable. Her new "menstrual crams" are doing a number on her. Dogs don't like her anymore. Her scars start growing white hair, and her sister tells her she's a werewolf. These kids have seen movies before.

Ginger starts dressing slutty and making out with boys. Her sister teams up with the delivery driver kid to have her own WOLFtober for research purposes.

Ginger grows a tail and fangs, dominates one of her classmates in his car, has sex with him, and then eats the neighbor's dog. She comes home with wolf fingers and a newfound penchant for violence.

Lycanthropy turns out to be sexually transmitted, so Ginger's boyfriend is in trouble. Brigitte's boyfriend uses their high school level biology to determine that some wolfsbane should cure it. They sell it at the local crafting shop!

One of their classmates comes over and accidentally kills herself in their kitchen. They cover it up, but it triggers a town-wide investigation. Ginger doesn't lay low, and murders her guidance counselor instead. Then the school janitor.

Her face finally begins to wolfify, but it's at a conveniently timed Halloween party, so she can mingle freely. Her sister and the delivery kid try to lure her back to her house where the rest of the now-proven antidote is. Brigitte gets mild lycanthropy along the way.

Ginger goes full foam-rubber wolfsuit in the back of the delivery van. Brigitte's boyfriend gets eaten by the strangly smooth and shiny foam-rubber beast, and the action pauses for the mandatory lull before the climactic ending, which consists predominantly of loud snarling while a foam wolf head waggles back and forth before the sororicide.