Charley refuses to believe that a polite and quietly dressed man is in fact the last Chief of Owahnanee Tribe and his disbelief is deepened when the Indian asks for permission to visit their Tribal Burial grounds which just happens to be the backyard of the Douglas House.
Sally has her hands full when her glamorous cousin comes to visit after being expelled from three colleges. She attracts so much attention from the boys that Uncle Charley uses his vaudeville make-up box to transform her into an ugly duckling.
Preparations for Mike and Sally's coming nuptials get confusing when Sally's mother arrives two months early and takes over organising for their wedding. The daunting list of chores she hands Mike sends him off into a dream world as he and Sally imagine how other cultures decide who can wed.
Chip meets a group of Vaudevillians at a black tie affair with Uncle Charley and loses his sneaker in a Cinderella-like adventure when he falls for little Alice Vail.
Charley has a visit from an old Australian acquaintance who quickly fires the boys' imagination with tales of a paradise in the South pacific. The adults wonder if he is in fact an expert confidence trickster as he cheats Charley with an unexpected legacy that is responsible for a trip to the tropical island of Cocoa Fuji for Uncle Charley, Robbie and Chip.
Tramp causes confusion in two households when he runs away from home for fear of a cat. Meanwhile pampered 'Prince', pet in the mansion of a rich socialite, undergoes a complete and mysterious personality change.
Steve is having nightmares and his vision of the future has a computer named Betsy join the family. It interferes with wedding plans when it selects different mates for Mike and Sally. Hoping to prove the computer wrong, Mike decides he will have Steve fill out a questionaire for his dad and his mother. His reasoning is that they will submit the two forms and the computer will pick someone else for their perfect match, thereby proving to Sally how wrong the computer can be. But lo and behold the computer mates Steve and Mike's mom.
Chip feels left out of things when he is the only member of the family not working either full or part time. But watching 'Davy Crockett' and dreaming gives him a remarkable solution to his problem - he takes in a partner in his trapping business.
Robbie's friend has a grandfather that trains horses, but on the day of the big race when the thoroughbred racehorse loses her mascot, a rabbit, she loses her speed. But once she hears Robbie serenade on the guitar, the mascot problem is solved.
Steve is to show important engineering plans to a British scientist on a rush visit to the United States. But soon disappearing blueprints and home-baked cookies can't both be blamed on Steve's absent-mindedness - they become a plaything for Tramp and his friends.
Charley accompanies Robbie and his date to a reading by an old pal of his, Maggie McSterling. She is a veteran actress and she and Charley recall their friendship during their vaudeville days. Maggie looks much younger than her age, and decides that Charley needs a vigorous course of rejuvenation.
To avoid being absent from the family longer than neccessary, Steve declines an invitation to stay at a luxurious mansion in Mexico. So his host flies down the entire family, giving Robbie the opportunity for a few sharp lessons in the conservatism of old Spanish chaperoning customs.
Chip dates an older woman and Robbie finds his ideas misinterpreted when the Douglas boys face the troubles of growing up. Meanwhile, Robbie tries to come up with a novel idea for the school float, and proceeds to demonstrate that teenage is just a time in life, but his speech, activities and clothes prove that it something much more, a lesson Chip also begins to learn.
Steve's plan for an Hawaiian holiday is cancelled when Chip develops a case of bronchitis, so Charley and the boys plan to bring Hawaii to him in the form of a luau in the garden complete with ladies that he would undoubtedly have met on board ship.
A top woman pilot is preparing for her flight around the world and calls on Steve Douglas to modify the design of her plane. Steve takes more than a professional interest in the plane he is preparing for a long solo journey—as well as the lady aviator planning to fly it.
Robbie's glamorous girlfriend invites him to the exotic Brookdale Country Club, and he resolves to put pressure on Steve to join, despite the fact that his father isn't much of a joiner.
Robbie follows the fad and buys an antique aircraft to impress his new girlfriend. Steve lets him go ahead with trying to restore it, convinced it will never fly but as it becomes more airworthy, Steve becomes concerned.
A young engineer finds his lost half-Korean daughter who is staying temporarily at the Douglas House. But Uncle Charley finds that she exhibits more the cunning of the orphanage where she was found than the wisdom of the orient.
With Bub permanently away in Ireland, Steve finally resorts to domestic assistance and the Douglas home is afflicted with a fiery dragon of a housekeeper named Fedocia. When Steve is desperately trying to solve the problem of getting rid of her the situation is saved by the arrival of Bub's younger brother Charley, a recently retired Ship's cook on leave. With Steve away on business and Charley about to leave for San Francisco, Chip is unhappy that he won't have a parent to come to his school's Open Night. The family soon learns that Charley's crusty disposition masks a soft heart.
Bub decides to leave for an Irish holiday to help his formidable Aunt Kate celebrate her 104th Birthday in Dublin. Son-in-law Steve eagerly offers to do the housekeeping, rashly declaring that if all women organised their work efficiently, it could be done in just a fraction of the usual time. A belief which is hardly borne out by his own demonstrations.
When their best friends' marriage heads for the rocks, Mike and Sally pause for a second thought about their forthcoming wedding. Mike and Sally try to reconcile them by arranging visits to a marriage counsellor.
Robbie breaks a leg on the football field and becomes the first patient of a dazzling French nurse. Robbie doesn't mind being hospitalized when the nurse in training lavishes attention on him. Her constant attention baffles Steve until he is warned that her interest in him is more than in her patient.
It's a comedy of errors when Mike sets out to make an impression on his future father-in-law when Sally's father returns from an archeological expedition. Mike is unnerved about meeting him but practically kills him with a little too much kindness and enthusiasm.
After acting as the subject for a stage hypnotist, Robbie decides that hypnosis could help in his latest romance, which leads to a chain reaction when they try it out on his grandfather Bub who consequently does a weird dance whenever someone whistles.
Robbie consults Sally about his latest heartthrob—and he's sure he's too young for the girl. Robbie alarms Sally when he appears to be in love with her, and Steve must persuade him to grow up overnight.
At the Lotus Blossom Cafe, Steve is impressed by the timid and beautiful proprietress. The elegant Chinese widow contemplates returning to Hong Kong, but the Douglas family show her the American way of life, hoping she will stay.
Robbie's new girlfriend offers to get him and his guitar an audition at a club, and introduces him to a strange new world of far out youngsters who comprise the audience. When Robbie becomes a smash his family struggles to bring him back from stardom.
Mike's life is complicated by the return of his old girlfriend Jean Pearson. He can't bring himself to tell her that he is engaged to marry Sally. Chip and Ernie keep Mike under surveillance to report to fiancee Sally.
Chip and Ernie get an interesting lesson in honesty, and dishonesty from the school bully, who volunteers an insight to the underbelly world of swiping school lunches. Chip becomes bewildered by the differing standards of honesty among those he knows and Steve must do his best to sort out the problem.
Political overtones arise in the Douglas house when Steve becomes escort to a visiting congresswoman. Meanwhile Chip must entertain a small girl who aims to be class president -- even though Chip is campaigning to be.
Steve brings a business associate home for a quiet weekend of work, forgetting a prior commitment to the Cub Scouts where he has promised to lead the Moose patrol. He frees himself to do a rush design job while the hopeless Mr. Summers learns painfully what it means to be a moose.
The Douglas family continues to revel in the fun in the Irish village of Farnsea, ruled by the formidable Aunt Kate. Steve realises that her wisdom is helpful when Mary Kathleen Connolly becomes infatuated with him.
Bub decides to use his winning raffle ticket to take the Douglases to Ireland to visit his relatives. While in the village of Farnsea, they stay with his redoubtable 103 year old Aunt Kate and Cousin Mickey.
Realising the need for economy, Mike and Sally decide that her shower will be productive of useful gifts for the kitchen, but Bub is all for romance but Mike's practical ideas meet resistance when Bub plans a bridal shower for Sally. Chip and Ernie manage to turn the shower into something very impractical indeed.
Robbie and Ernie find that women are full of surprises and not all of them pleasing. Robbie tires of his noisy rock and roll girlfriend and switches to a more dignified girl who has no time for the childish pursuits of her peers, such as football and sock hops. And unfortunately for Robbie Douglas, Lorraine is also serious about getting married and before he knows it, he's engaged! Can even the sagacious Steve Douglas find a graceful way out of this mess?
Steve sails aboard the S.S. Carolina in order to establish a business contract with a firm but his task is complicated by Robbie who has a vacationing job as a steward onboard the same liner. They both find that business and pleasure do sometimes mix.
