One of the many movie posters on display in Dr. Mason's house is for the thriller, The Suspect (1944), starring Charles Laughton. This is significant, as the structure of "The Suspect" prefigures the formula for "Columbo", presenting the viewer not only with a killer whose identity is known from the outset, but also a seemingly mild-mannered and polite police detective who befriends the killer and knowingly uses him as a sounding-board for his various theories about the crime. It is the close relationship between killer and detective thus formed that leads to the resolution of the story. It is not known if William Link and Richard Levinson, creators of "Columbo", ever saw this film.
Rosebud, the sled made for Orson Welles's classic film Citizen Kane (1941), was one of three balsa versions made for the final scene of the movie. It happens to be the only one that survived the filming; the other two were burned in filming a scene in which a workman tosses the sled into a furnace.
The stage and theatre where Dr. Mason delivers his motivational speech has golden curtains and distinctive stairs on the right side. It is the same theatre where Dr. Keppel shows his movie with subliminal cuts in Double Exposure (1973).
This is the second episode (Troubled Waters (1975)) where the murderer has his pulse checked after committing the crime and, of course, his heart rate has risen, which is noticed and used as evidence by Columbo.
At the "W.C. Fields Bar" within the exclusive Hollywood Magic Castle, a plethora of Fields memorabilia is on display. In the bar, behind glass, is the original pool table that W.C. Fields used on stage. It's over 100 years old and is on loan courtesy of Everett Fields, Fields' grandson.