The odds are that you don't. Part of the reason that it was such a bad episode is related to theme. You want to incorporate themes into your games without making them laughable instead. It helps to know just what a theme is.
Themes are the framework from which plot elements hang.
Without a thematic frame of reference, literature is muddled, confusing and ultimately unfulfilling. With a theme in place, a work of fiction has cohesion. The same applies to role-playing games. Without a theme an adventure is a disjointed series of activities with no discernible end. They can begin to be favorably compared to interactive literature of the best kind.