More inappropriate eating

I almost didn't learn my lesson from last time -- don't ask a toddler rhetorical questions about eating non-food objects, and beware trying to find humor in it:

Mama: What does Sleepy Man like to eat?

Isaac: Tapioca. [pause] Dirt!

Mama: Do you eat dirt?!

Isaac: Yeah! [pause] Eat dog food.

Mama: Do you eat dog food?!

Isaac: Yeah! [pause] No.

Mama: [getting nervous she's encouraging bad behavior] People don't really eat dog food, do they?

Isaac: No. [pause] Only dog.

Whaddya think? Was he making a joke, or just listing stuff he knows he's forbidden to eat? Or are those the same thing?