The fence between the Simpsons' and Flanderses' yard is missing.
Bart parks his lawnmower right in front of the window. In the next shot it is not there any more.
Lisa says that the handle of the Big Dipper points to the North Star. In fact, tracing along the handle gives an Arc which leads to Arcturus. From there, you can follow a Spike to Spica (in Virgo). To find the North Star (Polaris), follow the two bowl stars farthest from the handle, in the direction from bottom to top of the the bowl. (Following them the other way will bring you to the constellation Leo, which you can recognize by the sickle asterism.)
While Bob checks Homer's credit to see if he can buy the huge RV or not, it cuts to his QWERTY-format keyboard as he types. The keyboard has two E keys, instead of one E and one F.
Bob asks Homer if he's Roman, because he looks like a God, ".....sort of". He then proceeds to call Homer Zeus, who is a Greek God, not a Roman God.