Data's evil twin brother, Lore, is found on Data's home planet of Omicron Theta. Lore attempts to deliver the Enterprise crew to the Crystalline Entity, which killed all life on their planet.

Brent Spiner (Lore)
Biff Yeager (Lt. Commander Argyle)

• Troi does not appear in this episode.
  
• Data tells Dr. Crusher that he has an off switch, but he swears her to keep it secret.
  
• Lore and Data were created by Dr. Noonien Soong using Asimov's theoretical positronic brain. Lore is more "human" than Data. The colonists were uncomfortable around him and asked that he be replaced.
  
• Lore can also use contractions, whereas Data can not. After Lore is beamed into space and Picard asks Data if he is all right, he clearly responds, "Yes, sir, I'm fine."
  
• Lore makes a return appearance in the fourth season in "Brothers" and in the sixth season in "Descent", while the Crystalline Entity strikes again in "Silicon Avatar" in the fifth season.
  
• Lore was originally written as a female android, but at Brent Spiner's suggestion they made Lore an "evil twin."