Mikey came out of the shower soon afterwards. Jon barely noticed him passing by, but he decided to try something. "Mikey, get me a Coke from the refrigerator."
The boy obediently went away and returned with the Coke. There was only one problem: there weren't any Cokes in the refrigerator. There were some cans of generic cola that his mom had bought, but what Mikey returned with was clearly a Coke.
In other words, the test showed that the wish worked. Mikey would do what he told him. Even if it's impossible. But was there a limit on what he could do? It's at least plausible that there's a Coke in the refrigerator. What if he asked him to do something clearly impossible. "Mikey, be president of the United States." No, wait, that might not work because the wishes have a limited range. He had to try something that was impossible, that happened right here, and could hardly happen under any circumstances without wishes....
