After Jones leaves Kollos' quarters, there's a cut to a reaction shot of Kirk with his hair parted in reverse.
At the end of the dinner, Kirk finishes off his glass, then the camera cuts to McCoy. Then it cuts back to Kirk and his glass is full.
Kirk aims his phaser at a berserk Spock's head and fires, but the beam hits him in the stomach.
At the beginning of the episode Kirk says they're taking the Medusan ambassador back to his home planet, but later Miranda says she's going to mind-meld with him when they reach a Medusan vessel.
Every time Miranda senses an intent to kill she gets an image from Larry's' mind of Kollos, but after the second time she asks him who or what he wants to kill - could it be...Kollos?
It is established that during transport of Ambassador Kollos, the protective visor must be worn to prevent insanity. In the final scene, when Spock transports the Ambassador off the ship, he wears his visor. But Kirk remains in the transporter room and witnesses transport without a visor.
McCoy: How can one so beautiful condemn herself to look upon ugliness for the rest of her life?
Miranda: How can one so full of the love of life condemn himself to look upon sickness?
Miranda: Ugly? What is ugly? Who is to say whether Kollos is too ugly to bear - or too beautiful to bear?
Miranda: (taking a rose from Kirk) I suppose it has thorns?
Kirk: I never met a rose that didn't.
Miranda: The glory of creation is in its infinite diversity.
Spock: And in the way our differences combine to create meaning and beauty.
Miranda: Joy can be many things.
Kirk: We all are vulnerable, in one way or another.
Kirk: Most of us are attracted by beauty and repelled by ugliness -- one of the last of our prejudices.
Kollos: You are so alone. You live out your lives in the shell of flesh, self-contained, separate. How lonely you are; how terribly lonely.
Kollos: This thing you call language, though; most remarkable. You depend on it for so very much. But is there any one of you really its master?
Diana Muldar makes her second appearance in Star Trek; The Original Series in this episode. Her first, being in "Return To Tomorrow". In later years, she will be in Star Trek: The Next Generation's second season as Doctor Pulaski, having replaced Doctor Crusher, from the first season.
The concept of Kollos, the Medusan whose physical appearance drives people insane, comes from the Greek legend of Medusa, who would turn anyone who looked at her to stone.