Howard freezes a little when he hears the kid's voice on the phone. He's never actually heard John, only seen him from a distance when his late-night jogs 'happen' to take him past the Chesterton household.

He has no idea how a kid who's never seen him can 'miss' him. It creeps him out.

So he plans of letting Barbara do her thing and then asking Ian if he can put the cats on the line. As a joke, of course.