Columbo secretly tapes his conversation with Dr. Mason, hoping to pick up the "kill" command. The conversation leads to the movie Citizen Kane and Dr. Mason, with relish, pronounces Kane's dying word, "Rosebud". At the end of the episode, when Columbo plays the tape for Mason, his pronunciation of the word "Rosebud" is distinctly different.
Although Dr. Mason's gate is said to be the original gate from the movie Citizen Kane, with the exception of the "K", it only vaguely resembles it. If you watch the movie Citizen Kane, you will notice that the real gate is much heavier wrought iron, and exceedingly more ornate.
At approximately 5:17 in the episode there is a scene of Kay (Trish Van Devere) in the bathroom wearing only a shirt. We are looking at her legs. As she moves, the shirt rides up and there have clearly been several frames cut from the film where perhaps too much of her buttocks were revealed (well, too much for prime time 1978, anyway).
when Kay Freestone is alone in lift after seeing gun on roof, she uses bent metal rod to pull gun over edge. while gun is balancing on edge camera shots swap from Kay to gun and every time gun is in different place.
When Columbo shows Paul Gerard Vittorio's appointment book, you can see that the exclamation marks near "M.Choy & M.Duvall" have been added in pencil, the rest of the entry being in ink. There appears to be a small exclamation mark beside "Duvall" in ink that was edged in, but it's not very clear, which probably led to the pencil additions.
Food critic Paul Gerard tells Columbo that Mary Choy owns "The House of Choy." But the sign on her restaurant reads, House of Shanghai. MaureenAbato