The Hollywood Knights," the motleyest imitation yet of "American Graffiti," illustrates how rapidly decay can set in after a concept is generally recognized as appealing in Hollywood. The idea of "American Graffiti" was rejected by every major studio (and some twice) before finally being shot for the paltry sum of $800,000 and released successfully in 1973.

Its success inspired a popular TV series, "Happy Days," which then became the model for increasingly strained spinoffs and imitations. "American Graffiti" no doubt paved the way for fitfully interesting theatrical disappointments like "American Hot Wax" and "The wanderers." The derivative trail seemed to come to a dead and last summer when George Lucas himself collabrated on "More American Graffiti," a misbegotten sequel to his original triumph. With "The Hollywood Knights," Floyd Mutrux, the director of "American Hot Wax," seems determined to wear out the welcome of a once-amusing nostalgic device once and for all.

"Knights" relies on a soundtrack full of golden oldies to evoke the ostensible setting. Beverly Hills on the Halloween night, 1965. The members of a car club, the Hollywood Knights, cruise in and out of their favorite meeting place, a drive-in diner called Tubby's that is scheduled to close the following day, victimized by uptight residents and urban renewal.

The jerky, threadbare continuity is devoted to savoring the antics of the most irrespressibly clowish Knights, notably an obnoxious campus cutup called Newbomb, embodied by a smirky galoot named Robert Wuhl. Sort of a cheerless, vague reminder of Dick Shawn, Wuhl betrays the ill effects of too many appearances as a facetious would-be escort on Chuck Barris' "The Dating Game." He already resembles stale comic goods in his movie debut. Moreover, he appears so old for the role that one is left with the impression that Newbomb must have been repeating the 12th grade since about 1950.

Evidently destined for a career as the slimiest lounge comedian in Las Vegas, Newbomb celebrates this farewell Halloween by repeatedly humiliating other subspecies: Gailard Sartain (who played The Big Bopper in "The Buddy Holly Story") and Sandy Helberg as stoogy patrolmen; Leigh French and Richard Schaal as adulterous upper-middle-class hypocrites; Stuart Pank as a fat adolescent mama's boy. The Newbomb repertoire relies all too heavily on stinky chestnuts: food-chuckling, mooning, flatulence, even the old flaming dog doo on the front porch. He's got a handful of hot ones, does Newbomb.

The derivative ineptitude of Mutrux's burlesque humor is epitomized in his borrowing of the sight gag from the cover of the National Lampoon's High School Yearbook Parody. You'd think that moving pictures might do more with the idea of a pantyless cheerleader than a still photograph could, but Mutrux is so imprecise and inattentive that the forgetful (or exhibitionistic) cute isn't even caught from wittly revealing, decisive angles. Mutrux canan barely be trusted to get a laugh out of can't miss, pie-in-the-face situation.

Mercifully, not every Knight is supposed to be a card. There are subdued subplots dealing with a member about to join the Army (and presumably perish in Vietnam) and another (Tony Danza of "Taxi") at odds with his girlfiend (Michelle Pfeiffer), a carhop with dreams of a Hollywood career. Although it comes as a welcome change of emphasis, the "serious" motif is as superficial and perfunctory as the farce. Nothing takes hold within this spastically facetious, centrifugal filmmaking context. Moreover, the dialogue tracks seem so poorly recorded or mixed that the conversation is often reduced to incomprehensible static.

Mutrux is probably a genuine child of pop culture, and he showed some comic aptitude in "American Hot Wax." He's backpedaling in "Holloywood Knights," a disgraceful trifle predicated on an idea whose time has passed. Far from showing continued promise, Mutrux has now identified himself as a kind of untutored, remedical-school imitator of George Lucas.