Commodore Stone is the highest-ranking Starfleet officer of color on the Original Series. The script explicitly called for him to be played by a "Negro" actor, which was standard for minority characters at the time. The actor cast was Percy Rodrigues who had already built an impressive resume of playing authoritative and highly educated characters. Interestingly, Rodrigues - just like William Shatner - was a Montreal-born Canadian.
Listed Trivia:
Dawson Casting: 25 year old Alice Rawlings as 14-15 year old Jame Finney. The space fuku outfit is seemingly there to make her look like a child.
Deleted Scene: In the shooting script, there was a scene (filmed but cut) where Jame Finney comes into the engineering room at the end of Kirk and Finney's fight. The appearance of his daughter and his wish to save her are why Finney tells Kirk where he sabotaged the Enterprise. The scene was presumably deleted because the episode was running long. However, the cut necessitated Kirk's voice-over log entry wherein he relates that a beaten and sobbing Finney tells him about the sabotage.
Referenced by...: Young Sheldon: In "The Grand Chancellor and a Den of Sin", after the revelation that he was being lied to, Sheldon is watching this episode and notes how Captain Kirk is not a real captain, just an actor (albeit a very good one).
Wag the Director: William Shatner was so concerned about the height difference between him and another actor (Winston DeLugo), that he made director Marc Daniels re-stage an entire scene, having the much taller guy sit at a bar stool instead of standing next to Kirk. (See also: "Who Mourns For Adonais?")
What Could Have Been: Sulu was scripted to feature, although, ultimately, his role in the episode was mostly given to Lieutenant Hansen instead (with a couple of Sulu's scripted lines spoken by Uhura in the final edit of the episode). And there's a nice moment where Uhura slides in to take the navigation station and made it look routine.
