CARS: No cars. From The Cars by Greg Cockerill.

Sightings: Our little dark-complected friend with the pencil-thin moustache—who often sits in the courtroom gallery—appears again in this episode. He is in the right rear corner behind Perry, and again whispers. The difference this time is that when Winifred Oakley and Dr. Douglas Keene enter Beverly Hills Doctor Hospital early in the episode, he is also sitting in the waiting room. Submitted by PaulDrake 33, 24 July 2008.
+ He is also drinking at a restaurant where Perry and Paul meet. We see the Pencil Mustache Man as the camera pans from the waiter making Caesar salad (with raw eggs) over to Perry and Paul’s table.
++ The Thin Man is eating at the Restaurant behind Perry and Paul. And the Distinguished Lady #4 is watching court from her favorite spot in the back row behind Perry. Submitted by BigBill767, 2/4/17.

Judy Lewis makes her only Perry Mason appearance playing Winifred Oakley. Judy Lewis was the daughter of Loretta Young and Clark Gable, the result of an affair on the set of the movie Call of the Wild in 1935. At the time Clark Gable was married to Maria Franklin Gable and Miss Young was unmarried. Submitted by PaulDrake 33, 24 July 2008.
+ She certainly has her mother’s wide set eyes. DOD 07/22/19
++ Knowing her parentage, you can certainly see her resemblance to both, that to Loretta Young being predominant, but there is definitely more than a suggestion of Gable there, too, though I can't quite put my finger on exactly what. OLEF641 12/17/2020
+++ I think it's her smile, and the ever-so-slight space between her front teeth. jfh 21Nov2023

John Agar makes his only Perry appearance here as Kenneth Baxter. John Agar is well known for being the first husband of Shirley Temple from 1945-1950. Submitted by PaulDrake 33, 22 February 2014.

Maxine Cooper plays Nurse Edith Devoe in this episode and portrayed Nurse Gladys Strome in “TCOT Fugitive Nurse” (#22). These were her only PM appearances, and she played a nurse in both episodes. Submitted by Charles Richmond, 10/24/2008.
+ MC has 42 IMDb Actress credits from 1948-80, including Nurse Evans in "Autumn Leaves [1956]." Mike Bedard 6.20.16
++ While not a "nurse" role, Maxine Cooper has a prominent role in the Mickey Spillane noir film, Kiss Me Deadly (1955). jfh 21Nov2023

Does Mr. Hilliard, the banker, look familiar? He might. That's Raymond Bailey who later achieved fame as banker Milburn Drysdale on The Beverly Hillbillies. Submitted by daveb, 5/14/2010.
+ Raymond Bailey has more banking connections than this. When Bailey first came to Hollywood to be an actor, he found it impossible to get work. Instead Bailey went into a high finance career working as stockbroker and banker. This according to his mini-bio at IMDb. Again, art imitates life. Submitted by Charles Richmond, 3/7/2012.

Character Names: Attorney Gordon Roland’s middle initial is “T”. It appears on the door to his office though it is omitted from the credits. Submitted by gracep, 8/20/2010.
+ Indeed there are more omissions. In previous episodes, the Autopsy Surgeon played by Michael Fox was Dr. Hoxie, though this name is omitted in the credits in this one. Additionally, the “Paint Store Clerk” is in fact A. J. Nelson, the proprietor of the paint store, who displays the stamp at the bottom of his paint can. Submitted by gracenote, 4/28/2011.
+ The address of the paint store, "2718 Clayton Ave, Los Angeles, Cali" is now in a residential neighborhood according to Google Maps. Submitted by Kilo 6/27/2017.

The Siamese cat owned by Hing (the eponymous caretaker’s cat) is named Monzu in the story, but the little feline did not receive any acting credit. Submitted by gracep, 8/20/2010.

Sightings: Through the courtroom door we see Little Old Lady in a Hat pausing in the hallway after the court recesses. One may see a glimpse or two of her during the hearing as well. Submitted by gracep 8/20/2010.
+In the same hallway view mentioned above, we can also see “Miss Carmody”, who shows up on the front row, prosecution side, during the proceedings. Other spectators include Distinguished Gentleman #1, Distinguished Lady #3, and of course, as pointed out in a trivia item above, Pencil Mustache Man. Submitted by alan_sings, 16 Oct 2010.

Monzu looks like the traditional, round-headed kind of Siamese cat. Around the time of Perry Mason (the 1950s), Siamese breeders started favoring more extreme triangular/wedge faces, and now a purebed traditional is rare. Submitted by gracenote, 4/28/2011.
+ The Traditional, sometimes called 'Apple-head', Siamese has undergone something of a revival and can be shown at cat shows that recognize them.. OLEF641; 10/17/2017.

Busy hospital: Dr. Douglas Keene worked in the same hospital where Dr. Michael Harris worked in episode 44 TCOT Curious Bride. Submitted by H. Mason 10/17/14

Movie: The Erle Stantey Gardner story that inspired this episode was made into the movie The Case Of The Black Cat with Ricardo Cortez as Perry Mason and June Travis as Della Street. It was released in 1936 and based on the serialized story with the same title as this episode that appeared in Liberty Magazine from June 1935 to September 1935. The movie is available on DVD. The only cat in the movie, named Clinker, wasn't black. Submitted by H. Mason 10/19/14
+ The movie bears a much closer relationship to the ESG source novel than does this episode. The episode changes the number of victims (from two to one), and the identities of both the defendant and the remaining victim. Toss in the novel's (and movie's) additional dead body and multiple killers and you have a recipe for a teleplay that significantly altered the novel's plot, but did not necessarily improve on it. Submitted by BobH, 17 October 2016.

This is the only PM writing credit for Richard Macauley who, according to Wikipedia, was very conservative and gave the HUAC names of Hollywood people he suspected of being communists...MikeM. 9/27/2016

This is the second of four PM appearances for Benson Fong (James Hing), who played Charlie Chan's Number Three Son, "Tommy Chan", in six movies. Benson Fong passed in 1987 at the age of 70. He was survived by his wife, five children, and nine grandchildren...MikeM. 7/9/2018