Quartered at Dawn (1999)

In the middle of an isolated wintry field, two lustful Gen-Xers get it on in the back of their toy-bedecked Mercedes, only to unwittingly find themselves in the last reel of a horror film gone horribly wrong. Not far away, a woman smashes her car into a tree, only to discover her leg is a shredded bloody stump. Hot on her heels is a faceless ghoul hell-bent on burying his axe in her skull. A tussle ensues during which bullets are fired and limbs are lopped off. Meanwhile, the young couple gets dressed and wipes the fog from their windows; only then do they become aware of the gory melee that occurred not ten paces from their vehicle.