Boy, howdy, when I get it right about something being awful, it's really awful; we're in a public setting and we got John being made into a bad guy because he a) wants to enjoy something in peace without Elly pestering him and b) he offers a solution that makes too much sense and is convenient. Also, one would expect that after the last panel, Elly would be told that Cathy Guisewite wanted her punchline back.
Panel 1: We find ourselves at a restaurant; as
Panel 2: He reads the dessert menu and asks her if she wants anything; she says "Oh, no; I couldn't."
Panel 3: We move forward in time to a second or two after the waiter asked
Panel 4: NotCathy pipes up and says "No, nothing else for me. Yes, I'm sure. Nothing."
Panel 5: He smiles as he starts to eat the thing; she frowns because it looks soooooo good and she wants it sooooo much but eating it will make her soooo fat so it's soooo unfair that she can't have one of her own.
Panel 6: This doesn't, of course, preclude the possibility of tasting it just to see; with that in mind, she asks him if he supposes that she could have a little bitty taste.
Panel 7: She smiles, takes another of what she calls a little-bitty taste and what I call a huge spoonful and says "Mmm....just another teensy nibble."
Panel 8: At this point, he's sort of ticked off at her for asking if he'd mind if she could have just a leeeeetle bit more.
Panel 9: He's so disgusted that he simply tells her to take the thing merely to have some peace; since she clearly plans to sample her way into eating at least half of it, she might as well have all of it.
Panel 10: Her response is to unhinge her jaw and ask what he's doing because she said she didn't want dessert.
Summary: First off, Elly isn't in danger of being fat any time soon; even thirty years down the road, her spare tire is of the bicycle variety, so to speak. Second, her little tiny samples are what, as I said, I call shovelfuls owing to the Pattersonian inability to moderate an appetite. Thirdly, she responds to common sense by retreating into irrationality and victimism. Finally, John is meant to be the bad guy because he clearly wants Elly to get fat.