No real reason for posting this; just...[shaking head e]
From a review on IMDB:
First, He Was Home Alone, But Now, Nobody's Home! (Get it? If you don't, I'll explain later).
...

Now about my summary line. I said that "First he was Home Alone, but now, nobody's home". If you don't get it, I'll explain. See, we all know that Macaulay Culkin was in Home Alone and in it he played a kid who was home all alone. But now "nobody's home". That's an expression about crazy and fargone people that means they're crazy or fargone. When you're referring to a person by saying nobody's home, you're saying he's got no sense, no reason, no actual consciousness or care of what he's doing. Thus, nobody's home! I sure hope you get it now.