The bezel of the small window of the doomsday box has two small holes at the top and the bottom, but in tighter shots of the box the bezel is smooth with no holes.
A tremolo effect (rapid oscillations in volume) was added to the dialog spoken by the Box Creature; however, this effect is missing from the Box Creature's final line, "You may take your daughter with you."
While pulling things from underneath the bed trying to untangle her stole, Mary clearly has something handed to her rather than her reaching in and grabbing it.
When the man delivers the wedding gift at the door, he tells the butler, "For the newlyweds," but his mouth isn't moving.