Revealing mistake: After Elliot talks to Beverly about the speech, Elliot walks to the right and becomes transparent, giving away the visual effects.
Revealing mistake: When one character's killed, stomach sliced open, you can see the wire yanking open the prop stomach to the left of the camera.
Revealing mistake: Clearly not Susan Blakely when she goes topless. Her hair suddenly becomes curlier, that's a body double.