He talks about that in the commentary for another comic:

Transcript:

The goal in any cartoon is to create that perfect marriage between the drawing and the caption (if there is one). And this cartoon, I feel, is a good example of when that goal is reached.

Visually, I wanted to capture the look and feel of a scene from an old Bogart film. (I would have preferred the elephant to be a little more hidden in the shadows under the staircase, but it’s difficult to pull off those subtleties in newsprint.)

But the caption had to accomplish the same dramatic touch. In general, it’s risky to write long captions that contain two or more sentences, because it tends to break continuity with the static image. I think this one works, however, because there’s no exaggerated action in the drawing. The elephant is speaking under his breath, and Mr. Schneider has turned around and frozen in his tracks. Even if this little scene were animated, we wouldn’t see much more movement than what’s captured in this cartoon.