This show is in my top 10 favourite comedies of all time.
The premise for this show is simple - 4 beings from another planet (Dick, Sally, Tommy & Harry) have been sent to Earth to view life on this planet. Along the way, Dick (the "High Commander") falls in love with a woman he works with, Sally tests the strength of mankind, Tommy goes through puberty (even though, on his planet, he is actually the oldest out of the group), and Harry - well... I guess you can say... ummm.... Harry is just Harry.
This show attracted a plethora of guest stars during it's run such as Roseanne, Elvis Costello, John Cleese, Phil Hartman and many others.
This show is sharply written - and before this show first aired, I never knew that John Lithgow could handle comedy so well.
A great show and a must watch if you enjoy comedy mixed with a touch of sci-fi.