The crew returns to the Amusement Park Planet for shore leave, but when their fantasies begin to go wrong, Uhura is taken prisoner by a robot. Upon learning of the death of the planet’s Caretaker, Kirk realizes that the planet's machines have taken control.

William Shatner (Captain James T. Kirk)
Leonard Nimoy (Commander Spock)
DeForest Kelley (Dr. Leonard H. McCoy)

George Takei (Lt. Hikaru Sulu)
Nichelle Nichols (Lieutenant Uhura)
Majel Barrett (Lieutenant M'Ress)
James Doohan (Lt. Cmdr. Montgomery Scott)

• The amusement park planet was first seen in the classic episode "Shore Leave".
  
• This is the first episode where Lieutenant M'Ress (voiced by Majel Barrett) has multiple lines of dialogue. Her speaking voice sounds like all of Majel Barrett's other characters, but she annoyingly ends nearly every sentence with a vocal purr or a growl.
  
• Spock mentions his mother is fond of the works of C.S. Lewis, author of "Alice's Adventures in Wonderland". This is explored in detail in Star Trek: Discovery season 1.
  
• James Doohan also voices the Thought Duplicator Master Computer.