After three years, the Big Giant Head has finally accepted Sally's request to have her body changed for a man's. For their convenience, the bodies of Dick and Sally are switched. Now, in each other's bodies, Dick and Sally must try and maintain each other's romantic relationships and get accustomed to the changes that their new gender brings, while waiting for their request to be switched back to be accepted. Meanwhile, Harry is left in charge of Happy Doug's when Doug goes on vacation, but becomes worried when a group of burly, tough-looking bikers arrive.

Mary invites the Solomons on a murder mystery weekend, thinking that it might prove a fun activity. However, she goes down with food poisoning and retreats upstairs to her room. Downstairs, meanwhile, the Solomons are horrified when the first murder takes place, believing it to be real and, annoyed at the apparent lackadaisical efforts of Scotland Yard detective "Inspector McAffrey", they decide to try to solve the mystery themselves.

Mary reveals to Dick that she has been observing his family for a number of years and that she would like to make a documentary about them, in order to show how the 'typical American family' has changed. Unfortunately, Mary's film soon begins to create tension among the family and accusations that Dick is an abusive father, Tommy is a bed-wetter and Sally is secretly a lesbian start flying around, so Harry decides to become an alcoholic so as not to be left out.

Mary is having trouble dealing with what she has just seen - Dick transforming Liam into a monkey, which he had done to stop him doing the same to the Earth's population. Dick consults the other Solomons and they decide that the best approach is to deny everything. Meanwhile, Mary meets with Nina and Judith, who confess that they believe Dick to be an international terrorist, so when Dick and Mary next meet, she demands that he tell her the truth about himself. So, Dick tells Mary that he and the others are aliens. Mary's reaction is first disbelief, then shock, and then she finds it sexy to be dating a spaceman. Elsewhere, the local store has been robbed and Sally catches Don hiding in the frozen foods freezer, where he admits that he hid because he was scared. Harry takes a different line and asks the shopkeeper Sam out on a date, but later runs into her working at a posh restaurant, where she instructs him to call her Samantha. Confused, Harry believes that he is dating twins.

The Solomons are struggling to take in the news - they have been ordered back home due to Dick's transgression with Liam. Dick's first instinct is to ask Mary to come, so he takes her to the planetarium before breaking the news to her that they are leaving, and asking her if she will join them. Meanwhile, since admitting his fear to Sally, Don has decided to quit the police force and open a muffin store, but Sally is disgusted by this career choice and decides to whip Don into shape - and turn him into a hardy police officer. At home, Harry and Tommy are attempting to organize a farewell party for the aliens, but have no money, so they decide to max out their credit cards and not worry about paying the bill, since they'll be halfway across the galaxy - they even hire Elvis Costello to sing Fly Me to the Moon.

The leader of an alien recon party on Earth discovers he has "feelings" for a professor.

The Solomons discover a brand of new collectibles called Fuzzy Buddies (a parody of Beanie Babies) when eating at a fast food diner, and Dick soon becomes so obsessed with collecting them that he begins to lose control of his family's finances. Tommy's coach is annoyed at his lack of team 'pep' and so makes him the school mascot - a giant owl called Hootie. Things goes wrong, however, when Tommy becomes so high on school pep that he attacks the coach.

When an obnoxious professor dies during a party in his honor, Dick finds the will specifies that he must deliver a “forthright and honest” eulogy about the universally despised academic. Tommy neglects his female pal August to hit it off with an “easy” cheerleader.

Dick receives a roundabout lesson in family values from Dr. Albright's loopy brother, who claims to have been abducted by aliens.

Dick discovers the consequences of unvarnished truth when he repeats some of Dr. Albright's unflattering comments at an academic committee meeting. Sally and Harry apply for driver's licenses.

While Dick and Harry take up painting (Harry's good; Dick isn't), Sally takes over the school bake sale with the gusto of Gen. Patton.

When Dick's evasive about his past, Dr. Albright suspects he's a '60s radical fugitive. Harry joins a CD-of-the-month club, and is swamped with CDs.

Dick decides the reason Harry is “odd” is because he lacks a father, and sets out nurture the suddenly rebellious Harry. Meanwhile, sparks fly when Sally meets the hostile mother of her boyfriend.

Albright gets a new office, much to Dick's chagrin. Sally lands in the hospital---where she, Harry and Tommy pretend to be “ER” doctors.

Homecoming's upcoming, but Dick can't seem to understand football's appeal. Tommy has a crush on his Glee Club teacher. Sally makes Nina her best friend. Harry gets a job as a security officer.

Dick's delighted (but Tommy isn't) when Tommy's accepted to a school for smart kids. Sally falls for a guy she met in a gay bar. Harry dabbles in magic.

Thanksgiving's an alien concept for the Solomons; it's an annoyance for Sally (who must cook), and an onus on Tommy. But Harry finds romance.

When Tommy asks Dick to direct his high school production of “Romeo and Juliet,” Dick takes the role a little too seriously. Sally tries to get Officer Don to fix Albright’s parking tickets.

While doing a favor for Dr. Albright, Dick sprains his ankle and discovers the power of guilt. Harry, desiring his own room, moves into a tree house. Tommy uses Sally to sell chocolate for a school fund-raiser.

Dick fears his relationship with Mary has grown stale. Tommy's growing tired of August's “perfection.” Harry and Sally switch jobs.

Dick, fearing that Mary has him wrapped around her little finger, takes lessons in being "manly"---from Harry. Sally and Tommy have a showdown with the game Monopoly.

While Dick cracks North Rutherford society (to Albright's chagrin), Tommy hangs out with school toughs. Meanwhile, "Mustang Sally" develops an interest in wrestling.

When an insulted Nina has had enough and quits, Harry becomes secretary to Dick and Dr. Albright. Meanwhile, Sally decides to live out the human childhood she never had.

A shy and brainy librarian is attracted to Dick, while Sally realizes why she's attracted to Officer Don. Meanwhile, Tommy and Harry write a “killer” episode of The X-Files.

The Solomons discover dreaming---and are shaken so much that they might have to go home for repairs.