Bob's celebrity clings to him like a threadbare bespoke suit, and he protects his dignity with the tarnished armor of irony. He has the aura of someone who might provoke a belated, befuddled double take after you've walked past him on the street. Who is that guy? I know I've seen him somewhere before.

Bob, you suspect, has grown accustomed to this reaction. He ruefully watches a few minutes of one of his movies, dubbed into Japanese and costarring a chimpanzee, on the television in his room. His newfound friend, Charlotte (Scarlett Johansson), a recent college graduate ignored by her photographer husband, makes snide reference to the supposedly great movies Bob made back in the '70s.

Now, he walks through the halls of the luxury hotel where most of the film's action — or, more accurately, its stasis — takes place as if balanced on a tightrope strung between arrogance and despair.

To those in the theater, of course, Harris' pockmarked pancake of a face will be immediately and gratifyingly familiar. He is Bill Murray, 52, now in his fourth decade as a ubiquitous pop-culture presence and yet still, somehow, a surprise, a paradox — even a mystery.

Murray's subtle, aching, witty performance in "Lost in Translation," which opens in Austin today, is certainly a revelation — and murmurs about an Oscar nomination have already begun. But it is hardly the first in his long and varied career. Wow, you think, this guy is an amazing actor, but such expressions of amazement have been bubbling up, with increasing frequency, for 20 years — at least since "Tootsie," in which he played Dustin Hoffman's hapless roommate.

Viewers (and reviewers) of that very grown-up, very funny movie were somewhat astonished that Murray, whose film work had consisted up to then mainly of very juvenile, very funny comedies like "Meatballs" and "Stripes," was capable of holding his own in such sophisticated company as Hoffman and Jessica Lange. The loudest such chorus came in 1998 when he played Herman J. Blume in Wes Anderson's "Rushmore," a performance that won him best-supporting-actor awards from the New York Film Critics Circle and the National Society of Film Critics.

Deservedly so, but to treat that film as a midcareer miracle is to ignore the still-underrated, altogether miraculous "Groundhog Day" (1993) and to sell short his consistently inventive, peculiarly affecting work in a mixed bag of comedies before that, from "Scrooged" to "Quick Change" to "Ghostbusters" — one and two.

The habit of underestimating Murray's skills may arise from the old prejudice against taking comedians — in particular former "Saturday Night Live" cast members — seriously as actors. It may be that people confuse the lazy, alternately irritating and ingratiating underachievers he has so often played with the man who plays them.

His line readings have a tossed-off, casual quality that makes it easy to overlook his uncannily precise timing. He is one of the best improvisers in movies, and his most sympathetic directors, from Sydney Pollack to Coppola, encourage him to make use of this gift, honed in the early, pre-"SNL" years on the stage of Chicago's Second City and on the air with "The National Lampoon Radio Hour."

But to see him as Polonius in Michael Almereyda's criminally neglected modern-dress film adaptation of "Hamlet" (2000) is to see the full extent of his spontaneity and grace. You can't make Shakespeare up as you go along, but Murray does just that.

And the result is that the character, and the play, take on a whole new coloration. Polonius, the pompous father and duplicitous royal counselor, whose accidental murder troubles neither Hamlet's conscience nor, in most productions, the audience's, is revealed to be flawed, bumbling and desperately human as he tries to negotiate the perilous demands of fatherhood and courtiership.

His most notorious speech, the catalog of useless advice that politicians and school principals occasionally cite in earnest ("this above all, to thine own self be true"), becomes improbably poignant. Murray's tone and facial expressions indicate that this Polonius knows his language to be inadequate, but it's also the only language he has. He is the biggest phony in the play, but because he is the only person who seems aware of his phoniness, he also becomes the most honest, and one of the most vulnerable.

And this has been Murray's secret from the start: to use the sketch comedian's distance from the people he plays as a paradoxical way into them. Initially, instead of following "National Lampoon Radio Hour" colleagues Gilda Radner, Dan Aykroyd and John Belushi to "Saturday Night Live," Murray joined the cast of Howard Cosell's mercifully forgotten prime-time variety show; he came to "SNL," rather inauspiciously, as the guy who was not Chevy Chase.

And their approaches could not have been more different: Chase, in the manner of Bob Hope, always played himself, with obligatory, redundant air quotes around anyone else he might impersonate. Murray wielded irony in the opposite direction — not to indicate his separation from the character, but rather to emphasize the disjunction between what we see of the character and what he thinks of himself. This basic, self-ironizing strategy has turned out to be extraordinarily versatile, and it is what links the obnoxious, cat-in-the-hat anarchists of "Stripes," "Caddyshack" and "Meatballs" with the vain, self-pitying and more often than not lovable midlife trainwrecks Murray has gone on to play.

In some ways, then, Bob Harris is just the kind of role we expect to see Murray in. Herman Blume, the soulful mogul of "Rushmore," who is also the melancholy, blunted apex of a multigenerational romantic triangle, has an obvious kinship with the drifting, dislocated screen idol in Coppola's movie.

On their middle-aged faces, the well-known, childish smirk looks like a sign of wisdom; their disinclination to take anything too seriously is not immaturity but the opposite. And like Bob Harris, quite a few of Murray's characters — the TV newsman in "Groundhog Day," the unscrupulous bowling champion in "Kingpin," the struggling playwright in "Tootsie," to name a few — have had vexed, eccentric relationships with fame.

The key to these people — their awfulness, their pathos, their absurdity — lies in the discrepancy between their images of themselves and who they really are. They are creatures of sublime self-delusion, their unshakable vanity permanently at odds with both their circumstances and the personalities they reveal.

And what makes Bob Harris such a sad figure, and also such an appealing one, is that his vanity seems shaken. We watch him drifting toward a resigned self-knowledge, and perhaps losing his hold on the immunity to embarrassment that has so often been the saving grace of Murray's fools, losers and outright nutcases in the past.

Which is not to say that the performance isn't funny. Those eyebrows still twitch in mockery. That smirk still directs our attention toward ironies and incongruities we might otherwise overlook. That doughy body remains an unexpectedly agile vehicle for physical comedy, as when Bob Harris does flailing battle with an aggressive call girl in his room and an unresponsive exercise machine at the hotel health club.

And there is that voice, so accustomed to whining, wheedling, blustering and babbling, which here veers from its deadpan Midwestern default setting to growl, mimic, twitter and, in one mesmerizing, world-stopping scene, to sing.

The setting is a karaoke booth, into which Bob, Charlotte and a gaggle of her Japanese acquaintances have drifted in the course of a long, drunken night. Murray sings two songs, Nick Lowe's mock-anthemic "(What's So Funny 'Bout) Peace, Love and Understanding" and Bryan Ferry's elegiac "More Than This."

The latter song clinches the mysterious connection between Bob and Charlotte, a bond that is so intensely romantic as to make sexual intimacy irrelevant. But at the same time, the sight of Bill Murray belting pop chestnuts inevitably calls to mind one of his earliest, most memorable characters: the airport lounge singer from a series of immortal "Saturday Night Live" sketches, a wildly untalented pseudo-celebrity whose repertory included the theme from "Star Wars" and whose m.o. was annoying, nearly to the point of physical violence, real celebrities unlucky enough to be in his audience.

You could say that Murray has come a long way since then, but you'd also have to acknowledge that he's come full circle, for that hapless singer was, in his not-ready-for-prime-time way, as complicated, as ridiculous, and also as sad and solitary a character as Bob Harris himself.

• 'Lost in Translation' Reviews