UFO occupants, perhaps

• Little aliens?
• Visitors from far, far away
• Roswell crash victims, some believe
• Some Wells creations
• Venusians and Martians, in brief
• Xenomorphs, e.g
• Space aliens, for short
• Org. that produces college entrance exams
• Martians, for example

Wikipedia Word definitions in Wikipedia
ETS is an abbreviation of: