"What if . . .?" historical jokes (what if Attila the Hun and Oscar Wilde met for drinks at the Algonquin?) always seem yeasty till someone actually brews them up, and the thickly chaotic "Insignificance" is no exception.

The "what if" goes like this: what if Marilyn Monroe, Joe DiMaggio, Albert Einstein and Sen. Joe McCarthy were all to find their lives intertwined one night? The movie begins zippily, crosscutting from Einstein (Michael Emil) in his hotel room, being badgered by McCarthy (Tony Curtis), while Monroe (Theresa Russell) cavorts on the set of "The Seven Year Itch." Her dress, buoyed by the wind from a subway, blows up around her head, and DiMaggio (Gary Busey) grimaces as the crowd explodes in a chorus of yowzas.

But if the amusement park curlicues of director Nicolas Roeg's dollying camera lend a splash to this opening sequence (augmented by the lush swing score), it never quite detonates -- the cinematography is glitzy but repetitive, the color curiously flat and inexpressive.

At any rate, it's mostly downhill from there. The whole idea of uniting this unlikely quartet is essentially playful, but Roeg doesn't see it that way -- he wants Drama. So the characters are reduced to their scars, via flashbacks -- Einstein, his guilt over the atomic bomb; Monroe, her lonely childhood in an orphanage -- while Roeg wrings his hands till blood runs from the cuticles.

The McCarthy character makes an unsatisfactory villain -- there's a simple-minded smugness to the way "Insignificance" skewers anticommunism, and if that weren't enough, McCarthy is made into a brute, a drunk and a sexual pervert as well. Some of which is true enough, but at this late date, isn't McCarthy-bashing a little easy? Curtis tries his best -- glistening with sweat, he looks like a snake that has just shed its skin -- but he just can't do anything with material this blockheaded.

Russell turns in a superb Monroe imitation. The movie's one bravura scene comes when, trussed up in her white halter, she breathily runs through her version of the theory of relativity for Einstein, illustrating it with dime-store toys. Busey has a wonderful scene too, playing DiMaggio as a hoarse simpleton twiddling with his baseball cards in bug-eyed joy.

But the movie is never as good as these two scenes, and Emil, who appears to have been cast for his hair, tends to deflate them -- he reacts to these mad monologues by grinning inanely, like the doting Chinese butler in some drawing-room comedy. By the time he meditates on his own insignificance, you barely care enough to disagree. Insignificance, at the Circle Dupont, is rated R and contains nudity, sexual situations, profanity and violence.