Peter Sellers stars as Harold Fine, a self-described square--a 35-year-old Los Angeles Lawyer who is not looking forward to middle age and his upcoming wedding. His life changes, however, when he falls in love with Nancy, a free-spirited, innocent, and beautiful young hippie. After Harold and his family enjoy some of her "groovy" brownies, he decides to "drop out" with her and become a hippie too. But can he return to his old life when he discovers that the hippie lifestyle is just a little too independent and irresponsible for his tastes?

An expedition of the "Petrox" company, is exploring in search of petrol. A strange island where they arrive is the home of a giant ape, King Kong, that is captured by the expedition in order to make money exhibiting it to the world. When in the U.S. the huge gorilla becomes restless, trying to return home...

Pete Stancheck inherits from his Uncle Jim Douglas a race car being stored in Puerto Vallarta. With his friend Davy Johns (D.J. to his friends) accompanying him to P.V., Pete is dismayed to learn that the car is an older model Volkswagen Beetle. But when Pete and D.J. see what the car can do and learn that it somewhat has a mind of its own, they decide to enter it into the Brazil Grand Primeo formula one race. En route to Rio de Janeiro, Herbie, the car, gets Pete and D.J. into one predicament after another as it tries to help its new friend, a streetwise orphan named Paco, who Pete and D.J. encountered in P.V. and who stowed away in Herbie's trunk. Because of these predicaments, Pete and D.J. end up requiring a quick influx of cash and slyly enlist the help of wealthy Louise Trent and her bookish niece, anthropology doctoral candidate Melissa, to be their financiers. Pete's role in the scheme is to woo the shy Melissa...