Continuity mistake: As Hank is having his discussion with Cotton in the Casino you can see Cotton's red (playing) chips in front of him. In one shot Hank stands up and the angle shows Cotton from over Hank's shoulder and the red chips look black and badly damaged. The next shot from the same angle the chips are back to being red and completely fine.
Continuity mistake: When Leanne first arrives, she kisses Luanne, and gets red lipstick marks on her. Later, when Leanne and Luanne are near the bathroom and Leanne says "I knew you would understand" (about Bill), she kisses Luanne, but there are no marks from her lipstick. Even if she mostly kissed Luanne's neck, at least part of some of the marks should show when Luanne turns to leave (after talking to Peggy).
Trivia: During Hanks's conversation with Bobby when he tells him that he will have to marry Luanne, look at the shelf behind Bobby. There is a Bart Simpson doll there. A few years before this was featured the Hill family was in the crowd at one of the pee wee football games in the Simpsons episode "Bart Star".