Two things:1. Humans can do this, too. It's called daydreaming. There is nothing unique or interesting or, least of all, funny about it.
2. What the hell is Marmaduke doing in a store?
Maybe Tolstoy started this way.
Golly, and now a joke about how health care is expensive.
This is actually another good example of using Twitter to tell a joke about something else, which in this case is the uncoolness of Sally and her friends.
Now Sassy deserves to die, too.