When Ginger and Fred meet in the case at the shareholders' meeting, they began to hiss and protract their claws and fangs. From behind, Ginger's fang is already out, and Fred begins to push his out. In the next shot, Ginger pushes her fang out for the first time.
The scenes at the farm are set in the winter, but the barn where Dren is living has sunlight showing between the boards making up the outer walls. It would be drafty and as cold as the outside, but is shown as warm enough to be livable.
The goof item below may give away important plot points.
Since the premise of the movie is based on science and not on supernatural or fantasy, Dren's flying ability can be considered as a mistake. Because it would be impossible for an animal that weighs approximately the same as an average woman, to fly with such small wings.