By trade, Bill Irwin is a funnyman; he also happens to be an excruciatingly funny man. Don't take my word for it--tune in tonight to his 60-minute public TV special, "The Regard of Flight," airing at 9 on Channel 26, and you'll catch him and his inventive colleagues, composer-pianist-ventriloquist Doug Skinner and actor Michael O'Connor, in their sublimely uproarious act.

What makes Irwin so distinctive, apart from the mysterious core of personal wit that gives any comic his individual stamp, are his range of means and the extraordinary physical components of his humor. His theater pieces, which he's been devising and performing since 1979, freely mix elements of clowning, mime, vaudeville, juggling, slapstick and circus horseplay, but it's also no accident that he's often worked with dance troupes. Like Jacques Tati, Ray Bolger, Steve Martin and many other essentially physical comedians, past and present, it's the way he moves--his features, his hands, his limbs, his whole body--that gives a special edge of hilarity to his every routine.

Film director Robert Altman, who used Irwin in his madcap "Popeye," has called him "remarkable, on the same level of genius with Keaton and Chaplin." That may seem extravagant, until you see Irwin go through his paces. His 1981 Obie Award termed him a "metaphysical vaudevillian," but he's also "popular" enough to have won a recent spot on "Saturday Night Live." Irwin's background has included theater studies at UCLA; training with the Ringling Brothers Circus; performance with Herbert Blau's experimental theater troupe, "Kraken"; and guest appearances with such outfits as the Oberlin Dance Collective. Every aspect of this pedigree is reflected in his current, original work--it's comedy, but it's got as many facets as a centipede has legs.

"Regard of Flight," taped live at New York's American Place Theatre, veers off in a multitude of merrily unexpected directions, but its springboard is a send-up of avant-garde theater. The script parodies both the mannerisms and the jargon of the genre. At one point Irwin delivers a manifesto, which Skinner promptly translates phrase by phrase into French. At another moment, Irwin replies defensively to a "critic" (O'Connor) who's badgering him from the front row--"This is a contemporary performance piece--it's postmodern--all the imagery you're seeing is laid within a formalist construct." But the heart of the material consists of hat tricks, chase sequences (through the audience and back onto the stage), disappearing routines and assorted predicaments and pratfalls.

Irwin's signature bit is his recurring exit, one leg slipping down and behind the curtain, sliding under as if being ingested by an invisible eel, until the rest of his body oozes afterward, helplessly protesting the while. Best of all, however, are the interpolated dance segments--Irwin's body looks like a parade float, he's so light on the feet; his legs dangle and flail in screwball frenzy, and his whole figure seems to be held together with paper clips. The character he projects is that of the performer-artist as innocent bumbler and, by extension, man as the flustered plaything of perverse destiny.

As a coda to "The Regard of Flight," Irwin performs five vignettes called "The Clown Bagatelles." Three of them--the most conspicuously physical--must be ranked as comedy classics: "The Swinger," in which Irwin's jiggling to rock music from a blast box goes totally bananas; "The Marionette," a tour de force of protoplasmic plasticity; and "The Waiter," in which Irwin, armed with a fork and plate, does heroic battle with a belligerent mass of spaghetti.

The live taping has its drawbacks--you want to feel part of the audience but sense your distance from it, and there are passages in which the continuity sags. One can't help but wonder what might result if Irwin were given rein to design a piece directly for video. But even this single, imperfect encounter with Irwin is enough to hook you for good.