Homer Simpson asks his 10-year-old son Bart to say grace at the family dinner table. "Dear God," says Bart, bowing his head and folding his hands, "we pay for all this stuff ourselves, so, thanks for nothing."

Why, you little -- -- !

Bart's back, in all his unadulterated audaciousness, and so is "The Simpsons," the irreverent animated sitcom from Fox TV that finally returns for a new season -- as full of wit and mischief as it was last year -- at 8 tonight on Chan- nel 5.

This season, as most of the expanding free world knows, "The Simpsons" airs opposite NBC's longtime Nielsen behemoth, "The Cosby Show." Much has been written about this supposedly monumental face- off. "The Cosby Show," it's been said, embodies the optimism and materialism of the '80s, whereas the Simpsons personify the sadder but wiser pragmatism of the '90s. Thus, Their Time Has Come.

Johnny Carson observed in a monologue that even though the idealized Huxtables on "The Cosby Show" are played by flesh-and-blood humans and the Simpsons are mere cartoon characters, "The Simpsons" seems more realistic. Family life at the Simpson home probably reminds more families of their own households than do the relatively homogenized antics of the Huxtable clan.

Whatever adjusted expectations they represent and whatever deep dark veins of cynicism and skepticism they have tapped, the Simpsons may truly have earned the title of America's favorite family. The characters are now established friends, and the show has become the kind of overnight classic that only television can produce. A Simpsonian institution.

The little darlings are also, of course, creatures of commerce, and Fox's decision to move the series from Sunday nights, where it reigned supreme, to Thursdays, where "Simpsons" reruns have made relative peeps in the ratings, is being both hailed and derided for its daring. It has also tended to infuriate many of those who work on "The Simpsons."

"Suddenly a show that was a hit is fighting for its survival," says a perplexed James L. Brooks, who, with fellow producers Matt Groening and Sam Simon, brought "The Simpsons" to life (and we do mean life). Brooks's credits include "Mary Tyler Moore" and "Taxi" on TV and "Terms of Endearment" and "Broadcast News" in the movies.

"We're not fighting 'Cosby,' " Brooks says. "We just want to get healthy ratings." Still, he recalls wistfully, "there have been two weeks in my life when a show I was associated with was number one in the ratings, and on Sunday night, we had a chance to be the number one show in the country. I don't think we have a chance on Thursday night."

Fox made the reckless move to help speed its growth as a fourth network. So far this season, Fox's success has been mostly in the imaginations of magazine writers. Its ratings have dropped sharply from last season as it expands from three nights of programming to five.

Advertising Age reports that Fox recently had to stop selling ad time because it has to fill so many upcoming commercial breaks with "make-goods" -- free spots given to advertisers overcharged for commercials on the basis of optimistic ratings projections. Now comes "The Simpsons," perhaps to the rescue.

Fox has put its faith, and much of its fortune, in this show. But the Simpsons are so much more than pawns in a ratings game. They are funny-mirror reflections of what's weird and askew in American society, characters who have achieved a level of affection beyond that of most sitcoms performed by mere mortals.

And unlike real actors, the Simpsons don't age, although Brooks says there has been thought of taking the ever-present pacifier out of baby Maggie's mouth this season and having her utter a first word. Daughter Lisa will definitely be celebrating her eighth birthday on one of the upcoming shows. She develops a crush on a substitute teacher at school, whose voice is that of an extremely famous actor whose name Brooks pleaded not be printed in a newspaper.

Suffice it to say, this actor would be at home as a rain man or a marathon man or even as a graduate of all the president's men.

In next week's episode, Homer sprouts a lush head of hair thanks to a baldness cure and suddenly rockets up the corporate ladder. While interviewing young women to be his secretary, he gets a phone call from worried wife Marge, who orders him to hire the next man who walks through the door.

Result: Homer finds himself with a gay male secretary -- surely a cartoon first -- whose voice is that of actor and playwright Harvey Fierstein.

In other episodes now on the drawing boards (or, having left the drawing boards, making their way through the assembly process in Korea, where the drawings are put together), Homer and Marge will flash back in time to their courtship, the entire family will be sucked up into a spaceship by hovering aliens (part of a Halloween trilogy), and Homer will be reunited with a long-lost brother.

The third episode, "Two Cars in Every Garage and Three Eyes on Every Fish," is a bull's-eye political satire in which the tirelessly evil Charles Montgomery Burns, head of the nuclear power plant where hapless Homer works, defiantly runs for governor when federal inspectors order the plant closed.

He says he wants to "get the government off our backs," meaning, of course, his back.

"Do you realize how much it costs to run for office?" Burns harangues Homer. "More than any honest man can afford!" He assembles a campaign team that includes a spin doctor, a makeup man and a mudslinger, and orders staff members to dig up dirt on his opponent, the saintly Mary Bailey -- surely by no coincidence the name of the character Donna Reed played in "It's a Wonderful Life."

Bart offers his unorthodox version of grace when the Burns campaign invades the Simpson household for a photo-op family dinner. When he learns about the plans for the visit, Bart exclaims, "Oooh, a media circus!" Lisa is also thrilled: "A political discussion at our table! I feel like a Kennedy!"

In tonight's premiere, "Bart Gets an F," our plaintively bug-eyed hero finally bites the bullet and cracks a book, but only because he has been threatened with the ultimate humiliation: having to repeat the fourth grade.

"Bart is an underachiever," explains a child psychiatrist to parents Homer and Marge, "and yet he seems to be -- how should I put this? -- proud of it." Hmmm, something about that phrase rings a bell. Oh yes -- a Bart T-shirt that says "Underachiever, and proud of it," part of the massive "Simpsons" merchandising blitz, has irked teachers in some cities because they think it encourages kids to be satisfied with failure.

Federal drug czar William J. Bennett has been among those condemning Bart's underachiever stance. Bennett bumbled into a drug rehabilitation center in July, saw a Bart Simpson poster and growled, "You guys aren't watching 'The Simpsons,' are you? That's not going to help you."

In tonight's installment, Bart really does try to improve his study habits. First he approaches class brain Martin Poindexter, a whiz at opening books but a klutz at throwing a baseball. Alas, Bart corrupts Martin instead of Martin inspiring Bart. "Life's too short for tests!" the hedonist convert declares.

Is this episode an attempt to answer all the criticism of Bart? "No," says Jim Brooks flatly. "But we're mindful of it. I do think it's important for us that Bart does badly in school. There are students like that. Besides, I'm very wary of television where everybody is supposed to be a role model. You don't run across that many role models in real life. Why should television be full of them?

"Somebody who wrestles with being bad and good and comes out both ends at different times is the way most people are," Brooks says in Bart's defense.

While Bart has been the lightning rod for critical bolts hurled at "The Simpsons" -- most of them from educators and parents -- Elizabeth Thoman, executive director of the Center for Media and Values in Los Angeles, says the worrying may be misdirected.

"If kids look up to Bart Simpson, we need to ask why we use television for all the role models in our society, a much bigger issue -- why kids don't get their role models from within families, schools, church groups, other places where kids gather," Thoman says.

As for the show itself, "I'm not one of the people who's alarmed by it. The fact that Bart is an underachiever and proud of it -- well, I'm afraid there are a lot of these children. What we should do is look at what we've done in families or at school to make some kids be that way."

There is, meanwhile, a growing belief in some circles that Bart Simpson is especially popular among minority children. Gordon Berry, professor at UCLA's graduate school of education and author of "The Socialization of the Minority Child," dismisses that notion. He says the fact that T-shirts sold on the streets of Washington and other cities depict Bart as a Kid of Color have to do with marketing, not sociology.

"I've not seen any evidence that African American youngsters are any more taken by Bart Simpson than the general public," Berry says. "Believe me, Bart Simpson is hot in Beverly Hills, and he's hot at Harvard. He's hot everywhere."

Only kids who are not underachievers are likely to parrot Bart's philosophy about underachieving as a matter of pride, Berry says. "Kids who are underachievers know it's painful. There is nothing funny and sexy about being an underachiever to them. It's not a badge of honor. It's a parasite inside.

"The people who will like that 'underachiever and proud of it' line are the kids who know all the answers in class. Underclass youngsters who wear those T-shirts only wear them because they're popular. They're not proud if they're underachievers."

Too much fuss over a cartoon show? "The Simpsons" does lend itself to interpretive calisthenics. Its topical satire can be more sharply barbed than "Saturday Night Live's," and each episode is riddled with cultural references.

A religious subtext seems quite apparent in some of this season's episodes. After praying in his bedroom for divine intervention to delay a history test ("Well, Old Timer ... "), Bart is shocked to find the prayer answered. Sister Lisa, the brainy one in the family, had scoffed that prayer is "the last refuge of a scoundrel," but when Bart gets his miracle, she tells him, "I'm no theologian. I don't know who or what God is exactly. All I know is He's a force more powerful than Mom and Dad put together, and you owe Him big."

"Bart Gets an F" is not only funny, it's touching. You really find yourself rooting for this bratty little drawing.

"Anybody could walk in on anything we do here and not realize we were working on an animated show," says Brooks. "On the shows where we're doing the job right, you forget it's animation. The characters are real to us. We all have different favorites. There's no smirking around the table when somebody says, 'Marge wouldn't do that,' or when the actress who does the voice of Lisa says a line is 'too rough' for her. In a way, the Simpsons run the show."

Although the humor on the show can be wicked and sly, Brooks rejects the term "subversive," lavished upon it by a recent magazine article. "We don't sit down to be subversive," he says. "One man's subversive is another man's brash. I don't think of it that way.

"My own individual take on it is that we finally found out what 'family entertainment' is, or should be. I've sat there watching the show with my folks and my young children and we all laughed at different things. I like that."

As part of its strange authenticity, "The Simpsons" is one show about an American family in which the family actually does something that most American families do: watch television. This rarely happens on other shows.

What do they watch? Homer gets awfully excited by the fact that it's "Big Gorilla Week" on "Million Dollar Movie." Bart and Lisa are delighted by a sadistic cartoon called "Itchy and Scratchy" that includes the decapitation of a cat, whose head is then blown up with a firecracker. Worse stuff has happened in many a "Tom & Jerry."

Then there's radio, a morning zoo duo named Bill and Marty -- "two grown men who can't get enough of each other."

The satire doesn't get in the way of the characters' lives, however, as they navigate their way through a modern world of so many perils as to be laughable. They have emotional lives, they have wants and desires. In a future episode, Homer asks Lisa, "And what does my little girl want?" and the easily depressed child answers, "An absence of mood swings and some stability in my life."

In another show, Homer talks to Marge about what he wants from life, his big dreams. She summarizes them for him this way: "seconds on dessert, occasional snuggling, and sleeping till noon on weekends."

Earlier on the same show, a reporter approaches Bart as he fishes from a stream. "Name's Bart Simpson, and who the hell are you?" says Bart in his trademark greeting. "I must say that in my day, we didn't talk that way to our elders," the reporter says. Bart replies, "Well, this is my day, and we do, sir."

It is his day, and all of the Simpsons'. And since we are them and they are us, that makes it our day too.