In this episode, Kirk (pictured) and his wife Luann are playing Pictionary at a dinner party with the Simpsons. The goal is to draw a picture from a prompt, and have your partner guess what the prompt was within a time limit.

Kirk and Luann's marriage is about to implode, and they have several rather public and awkward outbursts. In this scene, Kirk has to draw "Dignity" and have Luann guess. He gets frustrated that she can't tell what the drawing is, and implies that she's more stupid than the cat, who would surely be able to guess it.

He gets fed up and says something to the effect of, "Let's see you do better." She quickly sketches something out (obscured from camera), and the guests at the dinner party all agree that her drawing is much more clear.

Part of the joke here is that Kirk can't draw dignity because he doesn't have any. It's an intentionally vague clue which you can't really draw a picture of. When Luann draws a clearer picture (at least, we assume it must be because the guests approve of it) it signals that she does have her dignity, which she later exercises by divorcing her husband.