"The Legend of Billie Jean" is trashily manipulative and utterly preposterous, so much so that, until the end (when it begins to sour on you), it's a thoroughly enjoyable hoot. Add a splendid cast and good air conditioning, and it's a perfectly mindless way to spend a muggy summer evening.

When Binx Davy (Christian Slater) has his motor scooter trashed by the town bully, his sister, Billie Jean (Helen Slater, and no relation) goes to the bully's dad, one Pyatt (Richard Bradford), with an estimate for repairs totaling $608. Pyatt fils refuses to settle up, Pyatt pe re sets to pawing the poor girl, and after much groin-kneeing and an accidental shooting, Binx, Billie Jean and their chums are on the lam.

One night, Billie Jean chances on "Joan of Arc" on the late show. A light bulb appears over her head (more or less), she sets to her tresses with scissors, and the next day she's appearing on the news via homemade videotapes, demanding the $608 and braying "Fair is fair!" This pithy maxim becomes the cri de coeur for the local adolescentry, children's armies march the streets stamping out child abuse, and Billie Jean T-shirts and the Billie Jean cut become just the things to wear to the mall.

"The Legend of Billie Jean" is partly intended as a satire of the American machine of celebrity, but it's mostly supposed to be taken straight, and much of the fun of the movie lies in trying to tell the two apart. Executive producers Peter Guber and Jon Peters ("Flashdance," "Vision Quest") have come up with a formula so invincibly rigid it inevitably descends into self-parody, but their movies never tip you off as to how aware of this they are. Billie Jean knees somebody in the groin (three times, actually); is this a "stand up and cheer" moment or a parody of a "stand up and cheer" moment? Billie Jean cuts her hair, and it becomes a fad: is this a satire of fads, or an attempt to start one? Well, sometimes it plays like satire, but in a movie so dense with market tie-ins (for the motor scooter, among others), it's hard to tell.

Guber-Peters movies may be profoundly boring, but at least they're not boring on the surface. They move. Scenes never go on for very long before a car is laying planks of rubber and Pat Benatar is wailing the theme song, "Invincible," for the fourth time; director Matthew Robbins loves his close-ups of sprinting sneakers. The movie has something of the full-bore energy of a Roger Corman car chase movie -- it's a sort of "Grand Theft Scooter." And it actually looks good -- cinematographer Jeffrey L. Kimball bathes his nighttime in vibrant indigos, and there are stunning canvases of the Texas landscape at sunrise, as freeways wind through the flatness like the condensation trail of an F14.

"Billie Jean" assembles a cast that's at least too good by half -- it's like watching the Group Theater run through "Home Sweet Homer." Helen Slater has curves that hug the summertime, and a sweet, saucer-eyed ingenuousness that creates an automatic immediacy with the audience that almost makes you want to join the children's army and follow her.

That's a big "almost" -- even Slater can't make all the fist-waving she has to do seem anything less than ridiculous. But she develops a nice rapport with Christian Slater, who has a goofy hell-raisin' steal-the-pie-from-the-windowsill charm, and with the deft Keith Gordon, who brings a nice combination of shyness and desire to Lloyd, Billie Jean's love interest.

Bradford bulldozes straight through the role of the heavy -- with a pencil moustache slicing through his bloat, he looks like Wayne Newton after a long night. As the DA, Dean Stockwell puts together a fun grab bag of winks, double takes and slow burns, all of which add up to "What am I doing here?"; Peter Coyote brings his gangly grace and Lincolnesque suffering to the sheriff. And Yeardley Smith brings such exuberance to Putter, one of Billie Jean's chums, that the cliche' of her role -- the foul-mouthed punk -- disappears. She sounds like Moms Mabley and looks like Broderick Crawford in pigtails.

Producer Rob Cohen is one of that die-hard group that wishes the '60s had never ended, and "Billie Jean" bears his mark, in its ersatz populism, its espousal of good-guy issues like child abuse, its evil politicos and trigger-happy National Guard, its condemnation of material culture. In the climax, everyone burns Billie Jean paraphernalia in a huge self-righteous bonfire; the mark of Pyatt's sleaziness is that, after the shooting, he goes right ahead and sells a poster of a scantily clad Billie Jean.

Which is, of course, what Guber and Peters are doing with posters of a scantily clad Helen Slater. "The Legend of Billie Jean" is one of those wiggy examples of collaborative artists working utterly at cross purposes; in "Altered States," it was writer Paddy Chayefsky and director Ken Russell, but here, it's the executive producers and the producer. Cohen chastises the exploiters while Guber and Peter exploit away. By the end, they're working together, doling out comeuppances with the tympanic dourness of Moses. But by then, you don't have to stand up and cheer -- you can just stand up and leave.

The Legend of Billie Jean, at area theaters, is rated PG-13; it contains profanity, some violence and sexual themes.