You may already be familiar with Garfield Minus Garfield by a guy named Travors. It reproduces many of the Garfield strips without Garfield or his speech bubbles. The result is Jon Arbuckle talking to himself and appearing to be even more of a desperate lunatic than he normally appears.
It's quite clever, and kudos to Garfield's creator, Jim Davis, for not bothering travors and allowing him to continue.
I think what Travors has tapped into is not unique. Comics, perhaps humor in general, is a light way of looking at what would otherwise be desperate, quirky, sad, or frustrating situations. Take away the punchline, and you're left with an unredeemed situation.
Take out one of your Calvin and Hobbes collections (Google some images, if you don't have one) and read each strip without the last panel.
It's often just as desperate, odd, and quirky as Jon Arbukle without a punchline. Read a whole book of Calvin and Hobbes strips this way and you'll begin to wonder why Bill Watterson added the punchline.
It's the bizarre without the humor that makes up so much modern literature, art, and film. It's the humor added to the bizarre that tries to make us feel good about the situation, rather than simply jarred. With humor we can laugh at the situation, rather than feel that what we are witnessing is a world spinning out of control.
It may be what separates art from less meaningful entertainment. Or it may be that there is a lot more art in our humor than we tend to notice.