When Homer decided to go back to get Bart, he enters the overpass from the bottom of the screen, yet exits from the top. And the sign still says he is heading to Las Vegas.
Lisa claims that the school orchestra's instruments are rusting seeing the damage that the steam does to her saxophone. Rusting can only happen to iron alloys, which instruments such as saxophones do not contain.
In this episode, Homer tells Bart that he is 38. This is not possible, as Bart is 10, and Homer was a senior in High School when Marge became pregnant with Bart. Therefore, Homer cannot be older than 28 or 29.