At times, cartoonists don't have a very contemporary idea to fill into their strips. This is the real test of their potential as entertainers.
Pearls Before Swine is a strip by Stephan Pastis. Its a pretty good one.
In this strip, the guy wearing the cap is Stephan himself (odd that he appears in his own comic strip, talking to his characters). The nasty rat and the fat pig are two of his characters.

Click on the image to enlarge.