Plot hole: The Simpsons take a flight to Washington D.C. for Lisa's speech. But it is revealed in a later episode that Marge has a fear of flying. This was before it was discovered that she had a fear of flying.
Factual error: When the piano keys are shown when it is played at the end of the episode, it is shown having one black key each time. Real pianos start off with three black keys, then two, then three and so on.