Lisa's carved head atop the log changes orientation between the vertical and the horizontal. When vertical it sits atop the log as if on its neck. When horizontal the head is facing forward, attached at the back of the head.
While reading a magazine, Bart says "Ah... Betty". But in the cover it reads "Itchy and Veronica".
The barber laughs after Bart realizes he was paid with hair. Then Bart leaves and the barber is still laughing but his lips and head are still.
When the tree is sliding down Lombard Street, the TransAmerica pyramid is shown in the background, to the west. The pyramid is actually east of that block of Lombard Street..