Trivia: When Kirk is donning the Gestapo uniform, Spock says, "You should make a very convincing Nazi." Although the look Kirk gives him is funny, it should be remembered that both William Shatner and Leonard Nimoy were both Jewish.
Trivia: The events and description of the Planet Killer in this episode are referenced in The Next Generation novel "Vendetta." It was in the records Data was examining for a report for Picard. The first one was called a prototype, and the one Picard and crew face is the finished model. Larger, more powerful, and warp capable, this machine was driven by the vendetta of a person that wants revenge on the Borg.
Trivia: This episode (which first aired on October 27, 1967) was the only "holiday-themed" episode of Star Trek TOS. It was supposed to be a Halloween-ish story with witches, a spooky castle, black cats, skeletons and zombies, and there are repeated references to Halloween and "Trick-or-Treat" throughout the episode.
The Ultimate Computer - S2-E24
Trivia: In this episode, when brooding about M5, Kirk quotes John Masefield, "All I ask is a tall ship, and a star to steer her by." In Star Trek V, on approach to the Enterprise-A, he again uses the quote.
The Gamesters of Triskelion - S2-E16
Trivia: The dagger that Uhura's drill thrall has on is the same model seen in S2: Ep 4: "Mirror, Mirror."
The Trouble With Tribbles - S2-E15
Trivia: Captain Koloth was played by William Campbell, who also played the fan favorite Trelane in "The Squire of Gothos." Almost twenty-seven years later, he reprised the role of Koloth in the DS9 episode "Blood Oath."
Trivia: Vulcans generally do not smile, but after Amanda says "I love you" to Sarek, then playfully chides him about it, he touches her fingers and smiles.
Who Mourns for Adonais? - S2-E2
Trivia: This is the first episode to feature all seven members of the original cast.
Trivia: The caves where the Children of the Son hide out are located right below the famous Hollywood sign.
Trivia: The Enterprise does not make an appearance until 27 minutes into the episode.
Answer: Kirk was getting his physical and Dr. McCoy probably turned off communications, because if he hadn't, Kirk would have left and headed straight for the bridge, leaving McCoy irritated.