Possible Clues:

• Roswell visitors?
• The Coneheads, e.g.
• U.F.O. crew
• Frequent 24-Down subject
• 1986 sci-fi hit
• That's what they are, even if they're evens
• Right to enter as asylum-seekers?
• Strange forms of life
• Margaret Mahy had them in the family
• To us, they're worlds apart