Mike and Sally are married as Tim Considine makes his last appearance on the show. Mike thanks Steve for everything before he and Sally head off to his new job out of state. Back at home, the attention turns to newly-orphaned Ernie.
With Mike & Sally married, the family prepares for Ernie moving on to his new foster family. Chip asks his father if they could take Ernie in rather than a foster family. When the social worker arrives, Steve considers asking her out.
Uncle Charley is upset when Robbie leaves for a date at 11:30 p.m., but Steve tells Charley not to worry because Robbie has commonsense. When Charley finds out he is dating a chorus girl, he is sure Robbie's future is doomed.
Steve takes the children to see the circus and they have a full day of entertainment. When Ernie wakes up overnight saying he sees a lion in the yard, Steve thinks it is just an overactive imagination. Then Steve sees the lion.
Chip has eyes for Mary Lou who is one year ahead of him in school. Mary Lou only has eyes for Robbie who is one year behind him in school. When Chip calls Mary Lou to ask her out on a date, she mistakenly believes it is Robbie and says yes.
Ernie volunteers Steve for a father & son show, but Steve is supposed to be out of town that day. On the day of the play, Steve changes his plans. Everyone goes to the school ahead of Steve, who is then stuck in costume and cannot drive.
Uncle Charley provides the correct answer to a radio contest and wins one dance lesson. His instructor is a pretty woman who is also skilled in sales. Charley buys her lines and purchases more lessons.
Robbie is recommended to take a ballet class by his football coach, to improve his coordination. All goes well, until Robbie is expected to perform at an upcoming ballet recital, against his "masculine" instincts. Will he perform?
When Steve has to fly to Hong Kong on a company plane for business, he decides to take the entire family for a vacation. Everyone is excited except Charlie, who is not sure he wants to see the modern city. He knew the city years before.
Charley overhears Steve on the phone arranging a marriage; Chip and Ernie learn he is arranging the church; and Robbie sees him at the jewelry store. More coincidences occur, all pointing to Steve getting married.
Robbie tells Chip that teenage parties are the best, so Chip decides he should throw his own party, with girls. Ernie is not invited since he is too young. As the party starts, the record player breaks. Ernie comes up with a solution.
Steve gives Robbie $50 to pick up his golf clubs. Since the store is not opened, Robbie goes to the pool hall. Two girls bet him to a game. They are pool sharks and win all Robbie's money. Charley plays pool shark and wins the money back.
A shaggy dog follows Steve home and does not want to leave. The dog loves Steve and sings howling songs to him, disrupting all the neighbors. Steve has a difficult time leaving the house to go to work.
Maggie Bellini, a wealthy businesswoman, promises to match the money that Bryant Park raises to build an art center. She meets the Douglas family and is interested in Steve. She tries to buy his attentions by giving gifts to the others.
Robbie saves Terri Wong from getting hit by a car. She tells Robbie that according to Chinese custom, she must do everything for him. He enjoys the attention at first, but it becomes awkward when she continues day after day.
Robbie meets a female explorer and she stops by his house. There the family meets her and she stays for dinner. Steve asks her out and they date while she is in town. When she leaves for another safari, she asks Steve to go with her.
Tina Cole plays Joanne. (In Season 8, she joins the cast as Katie.) Robbie & Joanne think being married while in college is easy when their friends seem to manage. They find it is not easy when they babysit the friend's child.
Steve and Chip deal with females in non-traditional male activities. Steve works with a female engineer who acts like a man and dresses in overalls at work. A female student signs up for the Track Team at school and Chip thinks it is wrong.
Uncle Charley tells Steve that Robbie is going steady with two girls. Steve talks to Robbie, but Robbie says he can handle it. One day, the two girls meet and start to compare notes on their very similar boyfriends.
After learning about the Statue of Liberty in school, Ernie decides to write a thank you letter to the French Ambassador in Washington DC. The Ambassador is touched, and invites the Douglas family to visit in Washington.
Ernie's girlfriend is an older classmate who is more interested in his stamp collection than him. Once she has the stamp she wants, the friendship is over. Meanwhile, Robbie is working on a school project but he has girls do all the work.
Ernie notices that a rare coin in his collection is missing and accuses Chip of swiping it. A kangaroo court is held and Chip is acquitted. Ernie then finds the coin and realizes Chip was innocent all along.