When the U.S.S. Enterprise is thrown into a time warp by a black star, it ends up orbiting Earth in the 20th century. A jet is dispatched to bring the "UFO" down and the plane is accidentally destroyed by the starship's tractor beam, forcing Kirk to beam the pilot, John Christopher, aboard.

Roger Perry (Capt. John Christopher)
DeForest Kelley (Dr. Leonard H. McCoy)
Hal Lynch (Air Police Sergeant)
Richard Merrifield (Technician Webb)
John Winston (Lt. Kyle)
Ed Peck (Col. Fellini)
James Doohan (Lt. Cmdr. Montgomery Scott)
George Takei (Lt. Hikaru Sulu)
Nichelle Nichols (Lt. Uhura)
Mark Dempsey (Air Force Captain)
Jim Spencer (Air Policeman)
Sherri Townsend (Crew Woman)

• Kirk tells Christopher that there are 12 starships like Enterprise, under the authority of the "United Earth Space Probe Agency."
  
• Kirk introduces Spock to Christopher as his "First Officer, Lieutenant Commander Spock" though he clearly wears the uniform of a Commander.
  
• The computer was upgraded on Cygnet XIV, a female dominated world. They gave the computer a sexy personality. It calls the Captain "dear", speaks seductively, and has the annoying tendencies to giggle and pout. (Apparently, women can't make professional computer systems!)