(at around 58 mins) When Betty is snipping some flowers in the wraparound story, before the final story, the buds are all closed. In the nest shot they're all open.
(at around 1h 29 mins) Position of the keys after Betty drops them in the final segment of the wraparound story.
(at around 3 mins) The position of the groceries in Betty's bag change between shots in the first segment of the wraparound story.
(at around 57 mins) After Drogan dies, he drops his bottle of pills. In the next shot the spilled pills and the bottle are differently positioned.
(at around 50 mins) The amount of whiskey in Halston's glass as he notices the gash on his shoulder.
(at around 5 mins) In preparing to cook Timmy, Betty remarks that she could never do long division and asks aloud how much is 75 divided by 12. When Timmy answers and asks why, she indicates that she is trying to determine his cooking time. But if she is, she must multiply 75 by 12. (The answer is 900, or 15 hours.)
(at around 57 mins) Drogan blinks after he dies.
When the camera is simulating the cat in first person, you can see shadows of strings that are on the camera.
(at around 58 mins) When the kid is going through the Tales From the Darkside book in his cell you can clearly see that the pages in the book are blank.
(at around 43 mins) Obvious fake cat as it attacks Carolyn's face.
(at around 50 secs) When the credits are being introduced, it's noted that the list is in order of appearance. However, Matthew Lawrence actually appears before Christian Slater and other names are obviously not in proper order.
(at around 42 mins) Kneepads on Amanda as she rolls downstairs.
(at around 1h 28 mins) In the wraparound story, Timmy and the witch both make clear that she's made him "eat cookies all day long" so that she can fatten him up while he's in captivity. He's visibly not fat.