Day changes to night and back and forth in the same scene, many times.
The car Stan is driving when they hit one of the the Eye Creatures is a white 1957 Ford Thunderbird. The close-up of the creature's severed hand is shown sliding off the bumper of a red Ford Falcon, which is Susan's car.
When the young couple wander in to the home, the girl opens a closet door and the contents spill out. The next shot shows the contents in the closet have been rearranged.
A zipper can be seen on the back of the eye creature's body.
When Stan and Susan are riding in car along with the severed hand, there is a very obvious string tied around of its digits being pulled to make the hand appear to move.
Many of the eye creatures wear only the head of the costume with a black jumpsuit and sneakers.
On some prints of this film, the title is the grammatically incorrect: "Attack Of The The Eye Creatures."
The classified briefcase in the opening scene is handcuffed to the courier's hand, but it's unlocked. If anyone flipped the latch the contents would have just fallen out.