Corrected entry: During the opening dream sequence on the "Planet of the Donuts", we get our first glimpse of the monster donut that will eat Homer when his shadow looms over Homer. In this shot the shadow is of a "regular" donut, i.e., one with a hole. In the next shot we see that the monster's hole area has teeth and is filled in with black; in other words, its hole is a regular mouth. As such it could not have had light shining through it to make the donut hole in his shadow.
Corrected entry: The Simpsons arrive back at their house and discover that the 2 carnival workers they let live with them have boarded up every window and way into the house. However, when they are in the tree-house, you can see the windows on the upper-floor have remained un-boarded.