After the scene where Marge tells the family that the soup is ready, they are shown in the next scene eating food off of plates instead of soup.
When Bart fakes stomach pains to get out of his History test, he walks down the hall past a door marked "MAINTANENCE", and enters a door marked "INEIRMARY", mis-spelt signs presumably permanently posted by school district workers (not student helpers).
When the citizens of Springfield are singing hand in hand after the snowstorm, one of them visible is Sideshow Bob, who had recently been imprisoned and hadn't been released yet.
The textbook Bart is reading says the First Continental Congress was debating over the Declaration of Independence when, in fact, it was actually the Second Continental Congress.