Guest, best remembered as guitarist Nigel Tufnel in “This Is Spinal Tap,” has returned to that classic’s “mockumentary” form to bring us Waiting for Guffman, a cinEma un-vEritE account of the casting, rehearsal and performance of Corky’s show. The movie is, from start to finish, a hoot. Directed by Guest from an outline he developed with costar Eugene Levy–which was then improvised by the terrific cast–“Guffman” is both a savvy satire of small-town boosterism and an affectionate salute to the performing spirit.

Resembling a cross between “Spinal Tap” and the 1975 beauty-pageant satire, “Smile,” “Waiting for Guffman” is a comedy for those who appreciated “SCTV” and get off on “The Larry Sanders Show.” Its humor comes not from jokes or plot twists but from the perfect pitch of its straight-faced performers, who never acknowledge that this “documentary” is utterly bonkers.

Guest’s Corky is a triumph, a queenly stereotype invested with such enthusiastic conviction it transcends offensiveness. (One of the unstated jokes is that it never occurs to anyone in Blaine that he’s gay: he’s just “artistic.”) The cast that Corky assembles is a classic: for starters, there’s travel agents Ron and Sheila Albertson (Fred Willard and Catherine O’Hara), whose audition piece is “Midnight at the Oasis.” The Regis and Kathy Lee of Blaine, they seem born to host a morning talk show. Less showbiz-savvy, but just as hungry for the spotlight, is the cross-eyed dentist Dr. Allan Pearl (Eugene Levy). Parker Posey plays Dairy Queen counter girl Libby Mae Brown, Lewis Arquette is the retired taxidermist who will serve as the pageant’s “Our Town”-ish narrator and Bob Balaban is Corky’s seething rival, the high-school music teacher.

“Spinal Tap” alumni Harry Shearer, Michael McKean and Guest wrote the show’s songs, which straddle the thin and hilarious line between competence and catastrophe. In a coda in New York, where Corky has opened his shop of showbiz memorabilia, the irrepressible impresario shows off his unique collection, which includes “action figures” from “My Dinner With Andre.” For more in that vein, rush instantly to “Waiting for Guffman.”