Peterson's Poi Juice is giving away a trip to Hawaii and Arnold Ziffel is chosen as the winner. When the ad agency rep meets Arnold and discovers he's not a human, he tries to disqualify the swine. Famous "pig lawyer" Oliver Douglas, as he's repeatedly referred to, is retained to fight for Arnold's winnings.
The Douglases are asked to donate old clothing to a charity rummage sale. Lisa is glad to give away Oliver's entire wardrobe, but can't part with any of her dresses. Each has a memory attached, leading to flashbacks of Oliver asking Lisa's father for her hand in marriage, the Douglases' honeymoon in Switzerland and their first party in their new Park Avenue apartment.
Fire Chief Joe Carson appoints Oliver as his assistant, assuming he'll pay for his trip to a Miami convention. Instead, Oliver's complaints about how the Hooterville Fire Department is inept and unprepared result in Carson being booted and himself being named chief. Not wanting the job or the grief he's getting for supposedly stabbing Uncle Joe in the back, Oliver finds a way to get himself canned--fining everyone in the valley for fire code violations.
Eb announces his engagement to Loreli Appleby, a girl he met the day before. In an attempt to impress his future father-in-law, Eb succeeds in destroying the farmer's cabbage crop. To get back in the man's good graces, Eb pawns Oliver's cow Eleanor so he can make the Appleby's mortgage payment.
Fed up with the lousy condition of the highway through Hooterville, Oliver launches an attack on their beloved state district representative, Ben Hanks. Oliver runs into a brick wall with the locals because Ben bribes them with expensive gifts; he even has a catalog for them to choose their "gifts" from. The folksy, guitar-playing politician proves too wily for Oliver, even after being caught padding the state payroll with relatives.
Wanting to be a bigger help to Oliver, Lisa decides to learn carpentry. She buys overalls and begins to study the craft from the inept Monroe brothers. Lisa's talents result in destruction in Monroes' workshop and earns Oliver a punch in the nose.
Oliver plans to leave Eleanor with Mr. Cowan's bull Dudley so she'll birth a calf and start giving milk again. Lisa complicates matters when she wants to make sure Eleanor has a good "husband" with bright prospects. No bull Lisa meets seems good enough to marry her "daughter."
It's "Old Mail Day" as Sam Drucker hands out letters that have gotten misplaced in his post office. He deliver one letter that dates back to 1917. Having learned nothing from his previous letter-writing fiascoes, an upset Oliver complains to the Postmaster General for delivery service. The locals soon turn on Oliver because Drucker's General Store is never open; his letter got the Hooterville post office reclassified and now Sam's always on his bicycle delivering mail.
The Agricultural Department is sending a student to learn the ropes from agent Hank Kimball. No one's too interested until Terry turns out to be an attractive blonde co-ed. All the men of Hooterville, eligible and otherwise, fall over themselves flirting and fawning. On the night of the big barn dance, the Douglas living room is packed full of maneuvering men, each thinking they're her date for the evening. Terry's choice turns out to be none of the above.
After Joe Carson quits as head of the Hooterville centennial celebration, Oliver gets the job. His idea is to stage a re-enactment of the town's founding starring himself and Lisa as Horace and Doris Hooter. In the dramatization, saloon girl Doris fleeces Horace out of the money he'd hoped to buy a farm with. Eventually, he gets his money back, thanks to her skills as a card shark, and they marry and settle Hooterville.
Lisa's convinced that Hungarian gypsies have placed a curse on her when she receives a dreaded blue feather in the mail. To "de-hexify" her, Haney sells Lisa a ridiculous recipe that she mixes up, places in a green purse, and hangs outside the front door. Eb gets a look at it and panics because the "green purse hex" will bring a drought. He counteracts it with his own concoction in a yellow purse. Oliver takes action to put a stop to all this foolishness.
After Oliver orders the Monroe brothers to finish work on the bedroom, they confess that they never got a building permit. Oliver storms off to get one himself, only to discover his barn is in Hooterville, but his house is in Pixley. Haney, who sold them the farm, offers to hook a rope to the house and pull it to Hooterville with his truck. Meanwhile, the locals turn on Oliver for having "moved" to Pixley. Fed up, he has the farm re-surveyed and gets even worse news.
For Lisa's birthday gift, Oliver plans to gets her a horse. Mr Haney delivers one, and it's not your average nag. Its name is Mr. Fred, a talking horse who's also a has-been TV star. Meanwhile, the locals decide that Lisa has a drinking habit and attempt an intervention.
It's Lisa's idea for her and Oliver to take separate vacations since they're getting on each other's nerves, but she misses him before she's out of the airport. Oliver's nerves are wrecked by her constant phone calls and the loony locals who think he kicked her out of the house. Fed up, he catches a plane to meet her; his layover in Cuba isn't planned.
Criminals rob a jewelry store in Chicago and stash their haul in a grain bin. The expensive gems end up packed in boxes of Crickly Wickly cereal shipped to Hooterville. Lisa knows real jewels when she sees them, but Oliver's sure they're just costume. After taking them to be appraised, the sheriff arrests Oliver for the jewelry store heist.
Recent law school graduate Brian Williams pitches Oliver on joining him in a new practice. After another of his patriotic speeches, this time about law, Oliver is ready to hang out his shingle. Lisa is excited about becoming their secretary, against Oliver's better judgment, and Eb is ready to take over running the farm.
The law office of Douglas and Williams is open for business, even though the sign has Oliver Mendell Douglas (later Oliver Wendell Wilkie Holmes) listed as a partner. Unqualified secretary Lisa destroys a office typewriter before having the new phone connected to a fire alarm "clanger." Later, to boost business, she advertises a grand opening special with free prizes and discount law services.
The Hooterville Young People's Agricultural Society, comprised of Eb, Hank and Arnold, flies to Washington, D.C. for the national convention. When the stewardess tries to throw the pig off the DC-3, the Douglases come on board to smooth over the problem. While Oliver tries to get the hiding Arnold out of "the occupied," the plane takes off with five Hootervillians aboard.
With the Douglases in Washington, the "Haney Farm Mindin' Service" leases out their house (for $4 a day) to a couple with six children. Meanwhile in D.C., Lisa and Eb go to the White House to have unannounced lunch with the president, Kimball causes chaos for the Secretary of Agriculture, and Arnold causes problems in a laundromat. Oliver calls an early end to their trip, forcing Haney to quickly evict the tenants who were secretly leasing the Douglas farmhouse.
After a friendly doe wanders onto the farm, Lisa starts a drive to ban deer hunting. When the governor arrives in Hooterville for the start of hunting season, Lisa presents him with her petition. He threatens Oliver and Lisa with jail time because her petition promises everyone who signed it a one-hundred dollar payment.
A check of their their marriage license reveals that Oliver and Lisa aren't husband and wife. They'd been mistakenly given a license to practice dentistry. Refusing to stay in the house with a bachelor dentist, "Dr. Gronyitz" moves in with the Monroe brothers until they can re-tie the knot. Their church wedding suffers on minor distractions considering Hank Kimball is the best man and Ralph Monroe is the maid of honor.
While all of Hooterville is excited about the upcoming big dance, Eb is obsessed with raising $20. He wants to buy his girlfriend a birthday present and take her to the "swanky" Pixley Diner (which has tablecloths). Oliver refuses to advance him the money, telling him to be ingenious. First, Eb begins leasing out the Douglas' wardrobe and telling folks that the couple's strapped for cash. After Oliver puts a stop to that foolishness, he babysits ten babies at once while their parents go to the dance.
From inside an old trunk Eb found in the barn, Lisa begins reading the diary of Lydia Plunkett who, in 1898, becomes a traveling saleswoman for a corset company. Lydia falls in love with rival salesman Harry Wright, whose career falters as a result of her success. The two marry, she becomes president of the corset company, and unhappily tends house. He eventually tires of being a housewife and leaves her. As Lisa continues reading, Eb is entranced by the story, but Oliver scoffs at the soppy romance.
Local inventor "Looney Luke" Needlinger has built a contraption that turns hay into milk. Convinced it will make them rich, Haney and Fred pitch Oliver on investing in the machine, but he thinks they're being conned. After seeing the milk maker in action, Oliver convinces a chemist to give the device a once-over. What he discovers insures that cows will always have work.
Oliver, Lisa and Eb talk about reincarnation after watching a movie about a grandfather who returns as a racehorse. Later, when Eb goes missing during a nasty thunderstorm, Lisa is worried sick that something bad has happened to him. She's greatly relieved when he returns home safely--"re-incarcerated" as a dog.