In Season 4, Ep. 8 "Chimdale", Stan is revealed to be bald and wearing a wig. Therefore, Stan's hair should not age with him.
Mount Kilmanjaro is featured with a pointy peak but in reality it has a flat plateau-like peak much like a table top.
When Francine throws Roger over the cliff and he yells at her saying he has the car keys in his pocket. But the car is running and the headlights are on. The car might have a start button.