The legal age to sit in an emergency exit row in a commercial jetliner is 15, not 13 as the stewardess on the plane states.
Hank states that he inherited his narrow urethra from his father, while Cotton distinctly says in another episode he inherited it from his mother. Of course, Cotton says a lot of things, including the claim that he can pass a bowling ball through his urethra.
A flight attendant says if Cotton doesn't calm down they will have to land the plane in Hawaii. A flight from Texas to Japan goes over Alaska, 2500 miles or so north of Hawaii.
The subplots regarding Luanne getting a second Bloodhound to replace Ladybird (who is not actually dead) and Bill and Dale getting arrested trying to make the Hill house look occupied are never resolved.