NO ACTOR CAN REALLY "play anything." That doesn't stop some from trying. However much they can go on about inhabiting -- or even getting carried away by -- a role, actors can't help dragging themselves, their personas, around with them from film to film. But some, eager for the challenge of something new, actually take on multiple roles in a single film, hoping to hide behind various wigs and accents, though certainly not so thoroughly that the audience can't detect and admire them in their different parts.

There have been some fascinating one-shots at this sort of thing: Alec Guinness, of course, in Kind Hearts and Coronets; Donald Sutherland's two-part debut, including a crone, in Castle of the Living Dead; Jack Nicholson in Mars Attacks! Even more interesting are those actors who've made something of a career out of such gimmick casting. Playing several parts at once would seem to be one sure way of obliterating forever a single, set persona; in fact, if they're any good, the actors can only recreate that image two-, three-, or five-fold, with variations, as it were, of their theme.

JERRY LEWIS

If Lewis was just a great film director (look, don't start with me, he really is), he'd be worthy of study and emulation. What makes him so fascinating, so wonderful, so goddamned unique is that this talent was immutably enmeshed with such a monstrous craving for recognition and love that Lewis cameos as himself in at least three of his self-directed features. (All of the films mentioned below are directed by Lewis.)

The cool, elegant genius behind the camera and the spastic, adolescent genius in front couldn't belong to the same body for long, so Lewis starting splitting himself up into smaller and smaller roles: himself and his mother in The Ladies' Man (1961), four would-be suitors in Three On a Couch (1966), a bank robber, a policeman, and a 15th-century monk in Cracking Up (a.k.a. Smorgasbord, 1983), six brothers and a kindly chauffeur in The Family Jewels (1965). Each of these brief parts is played as one broad note -- cretinous or absent-minded or loathsomely cruel -- and the Lewis-played protagonists tend to view each with a mixture of confusion and curiosity, as if he can't believe they're from the same species. All of these films are fascinating comments on and offshoots of The Nutty Professor (1963), where the nice-guy brainiac and the swaggering, thuggish Don Juan have far more in common with the public and private Jerry Lewis than with any pseudo-parody of Dean Martin.

PETER SELLERS

There's a degree of perfection, of laser-like precision, about Peter Sellers' various impersonations that's frankly inhuman. Different walks, different body languages, stunningly altered voices -- but nothing inside. It's as though he could only be so mercurial on the externals because he didn't believe there was any such thing as a soul to worry about.

Six parts in two Cold War satires show off both his range and his limitations: In The Mouse That Roared (Jack Arnold, 1959) he's an eagerly bumbling gamekeeper, a devious prime minister, and a charmingly dotty Queen Mum; in Dr. Strangelove (Stanley Kubrick, 1964) he's equally convincing as a stiff-upper-lip British officer, a milquetoast American president, and a lunatic German scientist. But with each of these roles, you're never in doubt how they'll react to any situation, because there's nothing surprising about them... I almost said "as human beings," but they're not that at all; they're more like wind-up animatronic dolls, each acting out their preprogrammed responses.

A similar robotic monotony helps make two later films shockingly lifeless: a dull king and duller swashbuckler in The Prisoner of Zenda (Richard Quine, 1979), and a forgettable Scotland Yard detective up against a merely silly (though apparently autobiographical, at least in his theatrical tastes) supervillain in The Fiendish Plot of Dr. Fu Manchu (Piers Haggard, 1980). As the one-man show in Lolita (Kubrick, 1962), however, he's riveting. Quilty's grubby comic-monologue energy flows through his two disguises: all giggles and stammers as the "normal guy" on the patio; aloof and all-seeing, even in the dark, as Dr. Zempf.

EDDIE MURPHY

As Murphy's career has waxed and waned, he appears more and more willing to conflate the popular with the bland. His lead roles are increasingly nondescript sweet guys who shamble through life with sad-sack smiles and low expectations. This is hardly what one would have expected from his brilliant stint on Saturday Night Live, or his dynamic turns in such early pictures as 48 Hrs. and Beverly Hills Cop, where he seemed the best thing to happen to comedy since the invention of the custard pie.

There were increasing signs of discomfort, however; the nicer the leads, the more vicious, nasty, and often hilarious are Murphy's trademark cameo roles. Even in the calculatingly uplifting Coming to America (John Landis, 1988), the barber shop scene where Murphy -- playing two elderly gents, one Jewish -- argues with himself over the merits of Joe Louis, feels much more raucous and lively than the dreary Prince and his love woes; this is where the film ought to be.

Vampire In Brooklyn, (Wes Craven, 1995) is a much better, if unoriginal, film than its reputation suggests. I suspect most of the disappointment came from Murphy's playing the title character rather straight, leaving the belly laughs to Kadeem Hardison, John Witherspoon, and Murphy's own sleazy criminal incarnation and even sleazier preacher. The best hope for the future, however, comes from the remake of The Nutty Professor (Tom Shadyac, 1996). The movie itself is terrible, but it's telling that only Murphy seems to have gotten the point of the original, making his Buddy Love as devastating an exposure of his own image -- loud, arrogant, cocksure -- as Jerry Lewis' was of himself. In his latest, Bowfinger, Murphy plays both a vicious Hollywood star and a nerdy relative who gets a break in show biz. Guess which one's the lead. Now guess which performance I think will be more interesting.