The set for the Heffernans' living room includes windows on both sides of the front door (the front door is centered between windows), but the view from outside of the front of their house shows the front door next to the right corner of the house with no window in between on that side (all of the windows are to the left of the door).
In the episode where Carrie boycotts Doug's favorite restaurant, Arthur receives a VHS box set on the Civil War (blue and red box). The boxed set is changed to "The Great War", World War I...different color (gold and white) and smaller package, too.
In one episode Doug and Carrie's wedding is shown. Here you obviously see Carrie's wedding dress. In a later episode where Carrie has become concerned with her weight, she is shown trying to fit back into her wedding dress. They are two completely different dresses.