Quote 22
Bunnies are TV but carrots are real. (1.173)
Because Jack only understands things (and people) he has seen in person, and because all his other knowledge comes from TV, he uses the word "TV" to mean "fantasy" or "imaginary." To Jack, anything that he hasn't laid his hands on is imaginary—even bunnies.
Quote 23
I think [Old Nick]'s doing sarcasm, when he says the really opposite with a voice that's all twisty. (1.429)
This is a pretty good definition of sarcasm, and it's impressive that five-year-old Jack not only understands what sarcasm is, but can pick up when someone is using it. That's more than a lot of adults are able to manage.
Quote 24
But I wasn't lying, only pretending. (1.517)
It's difficult to tell these two things apart. You can't really pretend without lying, and you can't really lie without pretending it's true. In Jack's mind, they're two distinct concepts. He doesn't understand that to an outside person, like Ma, they look like the same thing sometimes.