When Eddie has Karen White in the porno booth, he says, "None of them do. They're not real, the people here. They're dead. They could never be like me," but his mouth is almost always closed the whole time.
Werewolf Eddie needed to press the Play and Record button at the same time to record Terry's attack. But only the Play button was pressed down.
When Eddie is transforming into a wolf in front of Karen, his left hand turns gray and grows hair down to the knuckles. Then in the shot of his arm muscles expanding, his left hand has a normal skin color and hair only down to his wrist.
When Marsha makes the scratches on Bill's back, his back smooth and hair free. Yet the shot before showing them turning into werewolves, they were both covered with hair.
Crew or equipment visible
When Terry is in Dr. Waggner's office talking to Chris on the phone, there is an over-the-shoulder shot of Chris. Just before it cuts back to Terry in the office, a crew-member's shadow is visible moving toward Chris.
Slim Pickens is shot twice with the shots coming almost on top of each other in quick succession. However, he is shot with a manual bolt-action rifle making that impossible.
The book shop owner says a full moon is a Hollywood myth and werewolves can change whenever they like. He then adds they can only be killed with silver bullets, (which is another Hollywood myth). The filmmakers pick and choose, because silver bullets serve the plot later on.