When Hanky and Gordy escape from the school bus to climb aboard the feed truck, they do so through the side emergency exit. Not only does no alarm sound when this happens, it is closed in the next shot once they are aboard the truck.
Interstate 64 heads east from St. Louis all the way to Chesapeake, VA. Krugman states that he and Dietz were about to cross the state line. On the bus, it wrote Kansas City, Kansas. From St. Louis to Kansas City, they'll have to take Interstate 70 West.
The goof item below may give away important plot points.
In some of the last scenes when Luke and Jessica get together and then buy the Meadow Brook Farm, there is footage that was used in the beginning scenes such as the piglet standing in the feed trough and others.