Multi-millionaire Phillip Drummond, who has agreed to the death-bed wish of his housekeeper to raise her two small sons as his own, welcomes 8-year-old Arnold and 12-year-old Willis into his lavish penthouse. Anxious to make them feel at home, he showers them with gifts and love -- and is puzzled when he learns that the boys are planning to sneak from the lap of luxury back to Harlem. Aiding Drummond in his effort to make the street-wise, ghetto youngsters feel welcome in the affluent white world are Drummond's new housekeeper Mrs. Garrett and his 13-year-old daughter Kimberly.

Arnold's eavesdropping leads to trouble when a misunderstanding causes Willis and him to think that Mr. Drummond no longer wants them around; he has heard Drummond tell a social worker that ""black children belong with black families.""

Mr. Drummond's socialite and rather snobbish mother arrives and finds there's a lot she doesn't like about her son's new sons, but she soon learns a valuable lesson about what's really important in a person.

When Mr. Drummond tries to get Arnold and Willis into an exclusive prep school, it turns out to be just a little too exclusive for everyone's tastes.

Arnold ignores warnings and continues to drop water balloons from the balcony. Mr. Drummond's decision to punish Arnold for the prank with a spanking becomes a learning lesson for Willis too, when he insists that he be the one to spank Arnold -- but where's Arnold?

When Arnold loses his favorite doll, he makes sure that his misery is shared equally by the various members of his household, who soon try everything to get it back.

When Arnold is in trouble for putting his goldfish in Mr. Drummond's hot tub, Willis insists that it is wrong to convict him without a trial. The whole family, with Mrs. Garrett as judge, comes up with an important verdict.

Mr. Drummond and family gather around their Christmas tree and recall the many humorous incidents that the family has shared since Arnold and Willis moved in. This special one-hour episode features highlights from previous shows.

Mr. Drummond and family gather around their Christmas tree and recall the many humorous incidents that the family has shared since Arnold and Willis moved in. This special one-hour episode features highlights from previous shows.

Willis puts Arnold in training to fight the local bully, but Mr. Drummond insists more civilized solutions be employed.

Willis invites his neighborhood club from Harlem to visit, but things get out of hand when he tries to impress them with his new wealth.

Mr. Drummond's intention to marry an attractive widow doesn't meet with his children's approval, and Arnold, Willis and Kimberly devise a scheme they hope will turn his ""romantic"" proposal into a disaster.

A lonely Arnold comes up with a method of gaining his family's attention. Unfortunately his plan works a little too well; he ends up with everyone's attention, including the family doctor.

LaWanda Page guest stars as a cousin of Willis and Arnold who, after seeing the boys in their comfortable new surroundings, knows she should stay closer to her long-lost little relatives.

Drummond hires a tutor for Willis and Arnold who does practically everything but teach.

The kids devise a scheme hoping to make Arnold convince the new landlord to let the family keep the penthouse.

To get rid of his pesky little brother, Willis divides the bedroom in half and spends more time at his friend's house.

When Mrs. Garrett decides her life as a housekeeper is unfulfilling, she ends up being a guest in the Drummond home, and then makes an important decision concerning the future.

In order to earn the money to buy disco skates, and to prove a point to Mr. Drummond, Willis gets a job...but is fired on his first working day.

The stars of "Diff'rent Strokes" and "Hello, Larry" get together in a special, hilarious hour in which Phillip Drummond realizes that the purchase of a Portland radio station could mean the loss of a job for his old friend Larry Alder.

The crossover continues on Hello, Larry S01E10 The Trip (II).

When Arnold is witness to a hold up, the robber tries to ensure that the youngster will not identify him.

Willis is hurt when he thinks his family has forgotten his upcoming birthday. After dropping several unsubtle hints he discovers that not only has everyone remembered, but also his fondest wish has been granted -- a birthday party in his old Harlem neighborhood.

Mrs. Garrett visits Kimberly's school and takes on its pushy principal with surprising results.