Before being kidnapped, Betty leaves her friends house in her red Ford Pinto with the black top. Later, when the abandoned Pinto is found, the car is missing it's black top. It's now entirely red.
When Barnaby has finished his milk and is paying for it there's about an inch of milk left in the glass. When the camera view changes to behind him and quickly back to the front of him, the remaining milk in the glass has suddenly disappeared. The time lapse between the two shots did not allow enough time to finish off the remaining amount.