"THE SHAPE I'm in, you could send my body to science fiction," jokes Rodney Dangerfield, who's got a million of them in his zany comedy "Back to School," a feature-length celebration of the bawdy humor of this baggy-faced Borscht Belt clown.

In the age of the Nautilus human, there's something hugely appealing about the hero as fat slob. As puffy-eyed as Garfield the Cat and jiggling like a pocketful of change, the burlesque satirist plays a composite of his characters from "Easy Money" and "Caddyshack." He's millionaire Thornton Melon, who made his mint with a chain of Tall and Fat haberdasheries, and he did it without an MBA. Now he's going back to get his education. Of course, he gives better than he gets.

Nouveau-riche, self-made, loud, a big tipper, Melon does battle with the effete and the old elite wherever he finds them. Like Groucho before him, Dangerfield is at his best playing against straight society, humbling the smug with his audacious wit. As Melon, he has a field day. At a cocktail party hosted by his unfaithful wife (Adrienne Barbeau), a snooty guest admires the art: "Your wife was just showing us her Klimfft."

"You, too?" asks Melon, who has just torn out the center of a French bread and stuffed it with yuppie hors d'oeuvres. After a quick divorce from his adulterous social climber, he joins his son in his freshman year at school. The shy young Melon, played by colorless Keith Gordon, is being pestered by the frats at this ivy-ish university. Robbed of his confidence by their insults, he fails to make the diving team or get the girl. Dad intervenes, becoming the BMOC with gauche panache.

It's a tired old scenario that features the struggle between the classes, ending with the revenge of the nerds who teach the handsome blond preppies some humility. But Dangerfield is the ne plus ultra nerd, the nerd forefather. And he doesn't care. Inevitably, the roles reverse and the son parents the father, who gets a higher education in the finer things of life. But, don't worry, it doesn't last long. And Dangerfield gets back to being crass fast.

At the school book store, he buys "Shakespeares for everybody." He hires Kurt Vonnegut to do his literature homework and NASA for his son's astronomy report. He installs a wet bar and hot tub in his son's dorm room and engages bands like Oingo Boingo for nightly revels with the coeds. He asks one poetry major if she can help him straighten out his Longfellow. He's a sexist, he's a pig. But you laugh in spite of yourself because he's an audacious anachronism. Not that you'd want him to come over for dinner or anything.

"Back to School," cowritten by executive producer Harold Ramis of "Animal House" and "Meatballs," has all the earmarks of those rough-house lampoons -- breasts and low-brow humor. But in spite of everything, the movie gets high marks. No matter what class you're in, go on. It's "Back to School" time.

BACK TO SCHOOL (PG-13) -- At area theaters.