Final answer:
Perfect Strangers is the 80s sitcom that is NOT about a space alien. Mork & Mindy, ALF, and 3rd Rock from the Sun are sitcoms that revolve around space aliens.
Step-by-step explanation:
The 80s sitcom that is NOT about a space alien is Perfect Strangers.
Mork & Mindy, ALF, and 3rd Rock from the Sun are all sitcoms that revolve around the theme of space aliens. Mork & Mindy features an alien named Mork from the planet Ork who comes to Earth and interacts with humans. ALF follows the story of a furry alien named ALF who crash-lands on Earth and lives with a suburban family. Lastly, 3rd Rock from the Sun portrays four aliens disguised as a human family living on Earth.