Dick and Mary try to play a trick on her sister (Megan Mullally), but things don't go according to plan.
Mistakenly believing that Tommy and Alissa have eloped, Dick, Strudwick and Mary go after them.
While Dick and Mary double-date with Don and Sally, Tommy and Harry take to the road.
The Solomons find themselves leading different lives in a "parallel universe" — New York City. Richard Belzer, Tracy Morgan and Ana Gasteyer play themselves.
Dick encourages Tommy to attend the college where he teaches, while Sally tries to turn Officer Don into a success.
When Tommy goes off to college, Dick finds it hard to adjust, but Sally and Harry are quick to interview replacement aliens.
Dick joins Mary on an expedition, but doesn't dig archaeology; and renting his room strikes the other Solomons as a really "inn" thing.
While Dick and Sally form an act to entertain at children's parties, Mary and Harry get involved in Officer Don's self-defense class.
After a psychic tells him that he won't be around too long, Dick decides to find Mary a new lover.
Mary suggests that she and Dick spend some time apart, and Sally becomes the new weather forecaster at the local TV station.
Dick tells Mary's mother that she's a terrible mom; Sally and Harry are responsible for a new addition to the family.
After Dick and Don each buy half of a timeshare "luxury getaway," they take Mary and Sally on their first vacation there.
While Dick delights in a book that explains how to be truly happy, Sally goes to Tommy's college to try to help him out.
Dick tries to compete with Mary's secret admirer (John Cleese); the rest of the gang find their favorite movie's prequel.
Mary is having some trouble dealing with what she saw: Dick transforming Scoochie into a monkey. Dick inevitably tells her the truth and she has a hard time to believe in it. Eventually she accepts it and even becomes fascinated by it. When everything seems to be going fine for Dick, Harry announces that their mission is over and they are to leave Earth.
As a result of the manner in which Dick settled his dispute with Liam, the group is ordered home. Of course, there are always loose ends to tie up before a long space trip. Dick wants Mary to accompany them, and Sally decides to instill confidence in Don. They organize a farewell party, and Harry and Tommy decide to charge everything and not worry about being around to pay the bill. They even hire Elvis Costello to sing "Fly Me to the Moon."