Panel 1: Since Elly is stupid and won't take Farley to the vet to get a lecture about the dangers of just up and changing his food, she compounds her mistake by getting him something else he won't eat: the bag of low-cal dog food she's holding and yapping about when she tells Liz that they're all responsible on follow-through on the diet she imposed on Farley because reasons.
Panel 2: Mike and John make the scene when she decrees that this means no snacks, treats or leftovers and that she and Mike have to walk him after school every day until he collapses from starvation.
Panel 3: When Liz whines "Do we HAFTA?" because Farley is only 'her' dog when it's no hassle, Elly makes the mistake of asking them whose dog he is.
Panel 4: They all grin at her because he's just another responsibility that they've palmed off on her because it got boring.
Summary: Not only are they shitty pet owners, they have no problem dumping every crap job that's beneath them on her. Lovely family, eh?