There are tasteless jokes that offend society's professed beliefs; you might laugh at one, but when the unfairness of the premise is mentioned, yuou always say that it wasn't really runny. And then there are jokes that are tasteless in the sense of being flat.

"Under the Rainbow" combines both kinds of tastelessness: It has midget jokes, crotch jokes, Japanese squint-and-accent jokes, bosom jokes and cadaver (both human and dog) jokes, all stacked up like pancakes, and all just as flat.

The premise is that a group of actors hired to play Munchkins in "The Wizard of Oz" ruin a hotel called the Rainbow with childish and drunken antics, while various people run through trying to shoot one another for vague reasons having to do with World Wars I and II. These people keep mistakenly killing dozens of apparently expendable Japanese instead, and humorously propping their bodies in bars or hanging them from meat hooks in the hotel pantry. For example, the only genuinely kind person in the film, a Japanese whose graciousness is not the stuff of parody, falls into his salad, poisoned, and is seen from then on as a body with his face comically smeared with greens. a

Then there's the romance angle, which has Chevy Chase and Carrie Fisher attempting to fall into sex at first sight. They meet when he picks up the compact she drops and yells after her, "You dropped your diaphragm.

Trapped in this all-tasteless festival are Eve Arden and Joe Maher, who seem to have the idea for a funny routine about exiled nobility, which is not allowed to develop. Somebody apparently thought it would be even funnier to have their dog wetting people.

UNDER THE RAINBOW -- At the AMC Academy, Herndon, Hybla Valley, Inner Circle, K-B Rockville, K-B Studio, Laurel Towncentre, NTI White Flint, Rolling Valley and Showcase Fair City.