"Meatballs" is a tartly, unpretenciously funny as its title. A sort of "M*A*S*H" for campers, the deftly timed espisodic comedy is fabricated around the pranks, games, rivalries and lusts at a summer camp. As the seniors boys' counselor, an easygoing role model and spontaneous comic genius, Bill Murray of "Saturday Night Live" makes a deceptively sensational debut as a film comedy star.

Throughout the fusion of elements adapted from "M*A*S*H, "The Bad News Bears," "Animal House" and recollections and mischievous fantasies of camp. Mirry's cagey and enormously winning performance is the show's unfailing metal ticket.

Murry's character, called Tripper, sets the tone of the show by monopolizing the public address system at the camp. Affecting his laid-back deejay voice, Tripper can brighten the day with outrageous announcements, like "All junior girls are now junior boys" or "The State Fish and Game Department has just raised the limit on campers -- when you go out tomorrow, wear bright clothing and stay low."

Tripper is the benevolent, reassuring comic muse withing a society suffering from built-in impermanence and chronic inferiority. Camp North Star, Tripper's base of operations, is a harmless outpost of mediocrity, outclassed every year by its posh neighbor, Camp Mohawk, a hotbed of cuthroat competition and adolescent overachievement. Tuition at Mohawk is $1,000 a week, there's a two-year waiting list and every kid has to be voted in.

Oppressed by a long tradition of second-class status, amiable but lackluster North Star looks to Tripper for distraction or inspiration. The beauty of the conception, which wouldn't have been attainable with a comedian less gifted in the lead, is that Tripper's put-ons, practical jokes and pep talks do seem to generate healing, restorative community feelings. A crowd of nice but incorrigible tail-draggers relies on Tripper for a pick-me-up, and he invariably delivers.

Murray must have had a hand in writing his own material, in collaboration with screenwriters Len Blum, Dan Goldberg, Janis Allen and Harold Ramis (another alumnus of "Animal House"). It's good stuff rendered distinctive and foolproof by Murray's inspired timing and unpredictable wackiness. He roars off on at least two hillarious monologues, one a scare story told around the campfire at an overnight for counselors and the other a brilliantly conceived pep talk on the occasion of the annual camp Olympics between North Star and Mohawk.

But Murray is just as likely to knock you out in situations where the scene doesn't appear to be set deliberately for one of his show-stoppers. For example, there's a delightfully silly interlude on the way back from the overnight where Tripper seems to improvise a nosensical lyric. Suddenly everyone is singing it as the counselors canoe across the lake: "I love you and you love me/So let's walla-walla 'neath the mango tree."

Murray plays a wonderful necking scene with Kate Lynch, his strongminded opposite number the girls' counselors, and a memorable poker game with Chris Makepeace, cast as an odd kid out whom "tripper befriends, creating a witty, unsentimental rapport totally free of condecension. Director Ivan Reitman and the screenwriters haven't succeeded in working enough kids into the episodic continuity, but they exploit Makepeace astutely, portraying him as a shy outsiders positioned to come through with a clutch performance when North Star and Mohawk enter the last Olympic event dead even.

Reitman, the young Canadian who coproduced "National Lampoon's animal House," reveals surprising assurance as a director of this successor. If his ensemble does not collide with the acceleration and volatility of the brilliant young farceurs in Robert Zemeckis' "I Wanna Hold Your Hand," they are certainly lively and attractive.

The most amusing supporting performers are Jack Blum and Keith Knight as a Laurel and Hardy combination, a skinny wimp called Spaz and a porky goof called Fink, lovably sorry members of the North Star counseling staff.

Kids will obviously have a better time wathcing the sophomoric hijinks in "Meatballs" than they'd had slumbering along with "The Muppet Movie" a few days before. And if the situations and dialogue are occasionally racier than most parents might wish for a Pg comedy with considerable potential for entertaining juveniles, "Meatballs" is no more indiscreet on that score than "The Bad News Bears" -- of than loose-lipped old real life itself. CAPTION: Picture 1, Kate Lynch and Bill Murray; Picture 2, Bill Murray, second from right, at the annual camp games in "meatballs."