Related Clues:

• Xenophobe's fear
• With 27-Down, sci-fi phenomena that help explain this puzzle's theme
• Border crosser
• 1979 sci-fi thriller
• Nonnative
• From another planet
• One with a big head?
• Out of this world?
• UFO occupant
• Freakish
• Worf or Troi, e.g.
• Weaver's work
• Ufologist's study
• UFO passenger
• Klingon, e.g.