Fortunately for Cloris Leachman, Charles Martin Smith, John Vernon and Stephan W. Burns, the Walt Disney Studio discovered a generation ago that real human beings were cheaper than cartoons for feature-length pictures.

Fortunately for the Walt Disney Studio, someone there discovered about a dozen years ago that a film starring a Volkswagen bug is boxoffice magic, even when the characters seem to be making up the plot as they go along.

The 1980 result of these two discoveries -- the latest installment in the widely acclamined Disney Volkswagen cycle -- is "Herbie Goes Bananas," now at various theaters outside the Beltway (apparently the Disney people have given up on the inner city) with a cast made up entirely of humans except for one VW -- or more likely two, since Herbie, the hero, undergoes some striking changes of appearance in the course of the film.

"Herbie Goes Bananas" will be most viewing for those who have followed the four-cylinder hero's adventures since he first burst upon the world in "The Love Bug." Otherwise, it can be recommended to anyone who wants to see a Volkswagen win a bullfight, walk the gangplank on a luxury ocean liner, swim through the Panama Canal, foil the plots of a gang of bad guys who are trying to steal some gold Inca artifacts from a Central American country and use its radio antenna the way an elephant uses its trunk. As a bonus, the same viewers will see Harvey Korman get a pie in the face -- and presumably will enjoy it.

Those who have lived with a VW for any length of time know that the cars tend to have more highly developed personalities than most human beings. This fact is both the strength and the weakness of the VW cycle -- Herbie's fans will buy tickets whereever he appears, and if they are mostly half-price tickets, the high number sold seems to compensate for the low unit cost.

The problem for the human actors is how to play in the same scene with a VW without being totally outclassed. In this episode, it is more or less successfully managed by two members of the cast. Joaquin Garay III, playing a friendly, lovable, kindergarten-age pickpocket, manages it because he is cute as a bug. Harvey Korman, as the salty captain of a luxury ocean liner who dreams of the days of privacy and keel-hauling, manages it because he is Harvey Korman.

In one scene -- a costume ball on his ship -- Korman wears an archaic naval uniform and explains that is is an exact copy of "the uniform worn by Lord Nelson when he defeated the Spanish Armada." That's very funny, but one wonders whether anyone who understands why it is funny could enjoy the rest of the picture.