In the section where the school staff eats students, when Skinner and Lunch Lady Doris advance on Milhouse, Lisa, and Bart, Skinner's apron is off, then appears, then disappears and he puts it on again.
When Marge, Bart and Lisa are speaking with Ned, Marge's pearls are white instead of red.
After Skinner kills Groundskeeper Willie with the ax, he is wearing his apron, even though it is in the following shot where he actually puts it on.
When a machine picks up the Simpson house to take it to the 'Re-Neducation Center', the garage is on the wrong side of the house.
Bart's chainsaw disappears when he is speaking with Willie.
At the opening Marge Simpson announces that congress suggested the 1947 Glenn Ford movie "200 miles to Oregon". There is no such movie and in fact the only movie he appeared in that was released in 1947 was called Framed (1947).