This guy doesn't get paid enough. While he's a wild motorist—knocking over a statue in front of the McCallisters' house when he first arrives—the pizza boy delivers pizzas successfully and on time, working for a pizza place called Little Nero's (like Little Caesar's). What more could you ask for in a pizza boy?
He shows his appreciation for the tip Kevin's mom gives him—a polite and gracious young man. Yet, when Kevin orders pizza from him later, while he's home alone, he totally stiffs the pizza boy on the tip.
Does Kevin not respect the working people of America?
Pizza boy gets a raw deal, and, moreover, Kevin uses bits of the one gangster's speech from Angels with Filthy Souls to convince the pizza boy that he's about to get shot.
Which brings up another question—why wouldn't the pizza boy call the cops if he thought a gangster was shooting at him? Wouldn't they arrive and investigate the McCallister house?
But we probably shouldn't be examining the plot holes of Home Alone all that closely…or we'll be up all night.