There are pictures on the fridge of Don Geronimo and Mike O'Meara from the nationally syndicated radio show "The Don and Mike Show". The Reference to them not knowing who they were was an inside joke. They also guest appeared in the episode "Roamin' Holiday" (2.10).
All of the exterior shots of the Heffernan house are stock footage originally filmed for Sibs (1991) seven years before The King of Queens was filmed. The house is located at 519 Longview Avenue in Cliffside Park, New Jersey.
Executive Producer Michael J. Weithorn often sneaks his name onto the set. In one episode, Arthur attempts to sell the "Arthur's head screwdriver" to Weithorn Hardware and in another, Doug's dentist office is in the Weithorn Medical Center.
The trivia item below may give away important plot points.
Arthur is seen wearing a wedding ring throughout the entire run of the series even though his character is not married. That's because he's a widower on the show. In his real life he was married to Anne Meara (who played Olchin's mom on the show) for 52 years until her death in 2015.