According to a story told by casting director Billy DaMota in the documentary I Don't Know Jack (2002), the role of Fred the Cook was originally offered to Eraserhead (1977) star Jack Nance, who refused the role because he wanted to focus on his day job as a security guard.
The punch line to the unfinished joke the loudmouth at the bar was telling (It's the mailman's last day on the job, he goes to a woman's house and she invites him in, makes love to him, makes him a wonderful breakfast and then gives him 5 dollars) is: Mailman: What was that for? Woman: Well I asked my husband what to do for you on your last day and he said, "Screw him, give him 5 dollars." The breakfast was my idea!
The name of the burger shop that Julie works at is called "Fat Boy". This is a nod to the two atomic bombs dropped on Hiroshima and Nagasaki: Fat Man and Little Boy.
The real life Johnie's Coffee Shop, actually located on the Miracle Mile neighborhood of Los Angeles, closed as a real restaurant in the late 1990s. However, the building was never demolished and continued to be used for many other films. It was designated a historical landmark on November 27, 2013. It is now rented primarily for film and television productions as well as for pop-up shops and similar temporary functions. The building again gained notice in 2016 as a campaign headquarter for US presidential candidate Bernie Sanders.
Some three decades after making this movie together, after both of them had been divorced from other spouses, Anthony Edwards and Mare Winningham actually started dating in their private lives. They were married in 2021.