Stephen Pastis' Pearls Before Swine has featured many cameos from other comic strips. In addition to the humor such juxtapositions can provide, Pastis usually takes the opportunity to comment on the character that he folds into the sequence. In this case, it's as plain as the nose on your face. (click on image to enlarge)
Cathy Guisewit's creation Cathy (1976-2010) has no nose. Pastis call attention to that omission for the strip's punchline. When this oddity is brought to the reader's attention, it can lead to another realization. Every other character in Cathy was always drawn with a nose. Except Cathy.
For the comics fan, it's something to think about (albeit not too deeply). Thanks, Mr. Pastis!