When Kevin Spacey is working at Mr. Smiley for the first time (he is flipping burgers) he hears Katherine and "the King" ordering over the intercom. Then in the next scene it shows them laughing as they are pull up to the intercom. How could they order before they were even at the intercom?
At many establishments with a "drive through" service, there is a window/microphone/comical clown head for ordering, followed by another window for pickup/payment. This makes it harder to drive off without paying, and, in this case, explains the so-called slip up.
This is WRONG.
First, the guy hears the wife's voice ordering through the intercom, and THEN you see the car pulling over but they are not pulling over at the intercom, they are pulling over at the place where you pick up your order. That's why he sees her... aha!