LOS ANGELES -- Matt Groening's wallet sits there on his desk during the entire interview, and this is a wallet that's a wallet, a huge swollen thing stuffed with cash and credit cards. It seems to be throbbing, it seems to be glowing, it seems almost to be growing even as he speaks.

It's an animated wallet, in a sense; surrounding it and Groening in the room are, in various incarnations, the icons that changed his life: a "Simpsons" pinball machine, a "Simpsons" video game, even a "Simpsons" chess set, and lots and lots of Simpson dolls and figurines.

Matt Groening created "The Simpsons."

Tonight, "The Simpsons" ends its fourth season on Fox with "Krusty Gets Kancelled," an all-star revue staged to revive the collapsing career of Bart and Lisa Simpson's TV hero, Krusty the Klown. Johnny Carson, Elizabeth Taylor, Bette Midler and the Red Hot Chili Peppers are among those making guest appearances. Well, not exactly appearances; they supply the voices for cartoon versions of themselves. The Simpsons are America's First Family of Cartoonery -- unless you consider the Clintons to be cartoons -- and their weekly half-hour of satire disguised as sitcom is the biggest and noblest hit Fox has ever had.

It has made Matt Groening, 38, rich rich rich, and that can be a problem when you've come from nowhere, as Groening did about five years ago, and previously considered yourself part of the counterculture. It's just plain The Culture now, and Groening is a contributing and credit-card-carrying member.

"It's a real double bind because having gotten a lot of money very suddenly and still dressing like a slob makes me, for some reason, especially approachable by friends, relatives and strangers who want me to invest in all sorts of wild schemes," says Groening, rhymes with "raining," as he leans back in his chair. "The requests for money came in daily: 'Hi, I went to high school with you. Listen, I don't think they can extradite me from California; can you give me a job?' That's the way one letter went."

The money hasn't, he insists, changed him. He lives fairly modestly with his family in Venice, not Beverly Hills or Bel Air. He owns a tuxedo but says, defensively, that there are moth holes in it.

"I buy a lot more comic books and CDs than I used to," he says. "My friends and I, back when we had no money at all, used to wonder and say, 'Well, when we make it, are we going to start living the lifestyle we see on TV? Big mansions and all that? Or are we going to live exactly the way we live now, except a lot more clutter?' And this is your answer."

He waves his hand to indicate his fashionably messy office, on the second floor of a ramshackle building at the back of the Fox lot. James L. Brooks, the great writer, has an office across the way; it was Brooks and writer-producer Sam Simon who helped shepherd Groening's creation from a series of one-minute skits on the now-defunct "Tracey Ullmann Show" into the full-fledged animated sitcom that has captivated the country, and much of the rest of the world.

The show's big in Istanbul, Groening says, and his collection of Simpsoniana includes Simpsons-brand pasta imported from Australia and a poster of Bart doing a commercial for Japan Air Lines that plays only in the Far East.

"Back at the very beginning, when we were first talking about making 'The Simpsons' a series, I remember Jim kept on saying, 'What we've got to do is go for real emotions,' you know, try to avoid being cartoony. And that's what we try to do. We make all sorts of wild, exaggerated things happen to our characters, but we try to have them react the way somebody really would if he or she were in that situation."

The result is one of the 10 best sitcoms of the past decade or so and the most emotionally resonant cartoon series ever on television. It was genuinely touching, as well as funny, when mother Marge asserted herself by getting the lead in a local theater group's musical version of "A Streetcar Named Desire" ("Streetcar!"), or when baby daughter Maggie spoke for the first time, calling Homer "Daddy," with no one but the viewing audience there to hear.

Of course it's also been a gold mine. We don't want to stray too far from that fact. In 1991, Groening made Forbes magazine's list of the Top 40 richest entertainers, with total earnings for 1991 and '92 estimated at $18 million.

The merchandising alone has enriched Groening by millions: the Simpsons computer games, the Simpsons socks, the Simpsons comic books, the "Very First Limited Edition Simpsons Collector Plate" from the Franklin Mint -- $29.50 plus $2.95 shipping and handling. Limit one per collector.

Soon the pot will overflow even more. In January, "The Simpsons" went up for sale in TV syndication. That means that in the fall of 1994, reruns will begin appearing on local stations all over the country five nights a week. Some of them will play the show in the lucrative "early-fringe" period prior to their local news. Others will play it in the even more lucrative "access" time slot following the local news.

"This will be one of the best-performing sitcoms of the last three or four years when it launches," says Paul Bricault of Paul Kagan Associates, a media-monitoring firm. "Family Ties" earned $1.3 million per episode in syndication, Bricault says, and "The Simpsons" will probably bring in up to $1.8 million.

Trade-paper ads selling the program to stations feature Bart Simpson, the National Brat, at his familiar blackboard berth writing over and over in chalk "I will not let my competition grab the show that made Fox."

Groening is told that when "Family Ties" was sold into syndication, its creator, Gary David Goldberg, got a check for $40 million. Both eyes light up behind his thick glasses. "I'm sorry, this interview is over," he says abruptly. "I've got better things to do!"

He's joking. "I hear all sorts of crazy numbers bandied about," Groening says. "That would be really cool. I'll open my own theme park: Homer Mountain." Still joking. Or is he???

Miserable Grump

In person, Groening looks somewhat like a combination of two recurring "Simpsons" characters: Barney the bulging barfly and Marvin Monroe the portly bewhiskered shrink. He's approachably saggy and baggy, a bit guarded, somehow still kind of nerdily collegiate, although he's married and has two young children.

He sits at his desk compulsively, or perhaps anxiously, mutilating paper with a paper puncher. "Nervous stupidity," he explains. White dots flutter to the desk and the floor.

Yes, he got the names of the Simpsons from the family members he grew up with in Portland, Ore., in the 1950s. Dad was Homer, mom was Margaret. "I thought 'Marge' was funnier, and now she's got friends who call her Marge. They love it. They sign autographs."

Bart is, of course, an anagram for brat.

"The reason why the town is called Springfield," Groening says obligingly, knowing he will be asked, "is because when I was a kid I watched 'Father Knows Best,' which took place in a town called Springfield. And I always assumed it was the next town over.

"We get letters from people all over the place telling me they know it's their Springfield because their Springfield has a toxic waste dump and a nuclear power plant. It's very sad, the number of letters we get like that."

Homer Simpson works at a nuclear power plant where safety standards are not exactly strict. The nuclear industry has never been amused. A couple years ago, a "Simpsons" writer was quoted as saying the show was going to back off on that knock-nuclear stuff. Groening says baloney.

"The writing staff's made up of people with different political views, and whoever gave that interview at the time said, 'Yeah, we're backing off this.' That was somebody else. We used to hear from the nuclear people. The writing staff all went on a tour of a nuclear power plant at their behest. But I didn't go. I've been watching 'The Simpsons' too much, I'm afraid. But they went, and basically just got more ammunition for our show.

"There was this one sign on the door of a big utility closet, I don't remember the exact wording, but it was along the lines of 'If you hear loud, intermittent buzzing emanating from this closet, call your supervisor immediately.' And I just thought of Homer: 'Well it's intermittent and loud, but it's more of a siren than buzzing.' "

Groening marched against the Vietnam War and grew his hair long "and all that stuff" as a high school student in the late '60s and early '70s. Now, he says, "my politics are probably a little bit more screwy to the left than other people's."

There have been other rocky straits along the way. When the show started, the producers wrestled for control, attempting for a time to shove a groaning Groening out. "At one point, very early on, I was told to sit back, yeah," he confirms. "I ignored it."

He and Simon fought, especially that first season. Who won? "I don't know how to answer that question. I mean, nobody won. It's give-and-take. I won some battles, he won some battles.

"I've never heard of a Hollywood project in which there's not some sort of ego clash. And this show is one on which people were staying up until 2 and 3 in the morning, night after night, so that's the kind of thing that happened. But it never showed on the air."

Groening does not draw "The Simpsons." That is done by others. Some of the animation is done in Korea. In one episode, Marge painted a nude portrait of amusingly evil plant owner Montgomery Burns; his private parts were supposed to be blocked by the feather in a woman's hat, "but it came back wrong from Korea," Groening says, "so there is definitely a lost scene from 'The Simpsons.' "

Most of the other characters, however, have been seen nude from the rear on the show, another TV first.

Only in recent years did the thought occur to Groening that he would become rich and successful. Back in 1977, when he came to Los Angeles and worked in a record store across from a rock club ("all the bands came in and shoplifted"), he assumed he would be a struggling doodler for the rest of his life.

"I've drawn this way since I was a kid, but I never expected to make a living at it."

"What is 'this way'?"

"Simple and crude," he says. "And now I would say, crude but effective. I took great comfort in the work of James Thurber, the only cartoonist that draws worse than I ever did. The thing that inspired me the most when I was a kid was 'Rocky and Bullwinkle,' because the animation was crummy enough so that I could imagine doing something like that. I mean, it was primitive enough."

In a recently released issue of "Simpsons Comics and Stories," Groening writes an open letter to his fans, especially the young ones:

"During my formative years, nobody ever looked over my shoulder and said, 'I see promise in you, young man. Keep it up.' Cartoonist? I figured I'd grow up a miserable grump pulling a cart in a tire warehouse, making insulting caricatures on the walls of the loading dock when the supervisor wasn't looking.

"But I was ever so wrong. Which brings me to my message: Don't be a fool, stay in school and doodle."

Clicking Around

If only, Groening muses, "The Simpsons" were not on Fox but on a real network, one of the big three, with more and better situated affiliates.

He admits he'd prefer that. "Of course. It'd be nice not to be on Channel 94 in Montana. When you look at the ratings and then transfer those numbers to what they would be on a real network, I think it would be a huge, huge show."

"The Simpsons" started out on Sundays, one of the two biggest viewing nights of the week. Then Fox moved it up against NBC's "The Cosby Show" on Thursday nights when Cosby still reigned supreme. Everyone at "The Simpsons" was furious. Said coproducer Jim Brooks: "We could have been a Top 10 show if they'd left us on Sundays."

They've had to settle for the Top 20.

"Every single person who worked on the show was opposed to that move," Groening says. "I still forget to watch the show on Thursday nights myself."

Though still bitter toward Fox, however, Groening also thinks only Fox executives (especially former Fox Entertainment President Garth Ancier) had the kind of daring it took to put "The Simpsons" on the air in the first place.

"The fact is, none of the other networks would have agreed to run 'The Simpsons.' To me, it was obviously going to be a hit. If you clicked around with your channel changer, there was nothing else that looked like it. But Fox considered it very risky, and I don't think any of the other networks would have done it."

Once it was a hit, however, other networks, as is their habit, tried to imitate it, or at least tried to develop animated shows for prime time. "Fish Police" was a ghastly flop for CBS and "Capitol Critters" a mournful bomb for ABC. "I think they were sunk by incredible compromise," Groening says diplomatically.

He does, however, admire "Ren & Stimpy" on Nickelodeon, though he laments that creator John Kricfalusi has been reduced to the role of consultant and no longer has control of the program, the kind of thing that almost happened to Groening himself. Now, he says, he's "unbudgable" should anyone try any of that funny stuff again.

Work has already begun on next season's episodes of "The Simpsons." In addition, Groening is developing a spinoff, a live-action version of Krusty the Klown's show. He's asked if it isn't inevitable that the Simpsons will go the way of the Addams Family and someday become a movie.

"Oh the prospect of a live-action Simpsons movie is too horrifying," he says. "Macaulay Culkin as Bart? Ugh!"

He also continues to draw "Life in Hell," a cartoon strip syndicated to newspapers, and there's always the possibility that it could be turned into animated entertainment one day. And another Simpsons CD, "The Yellow Album" (as in the Beatles' "White Album"), is on its way.

And the Simpsons are, of course, part of Americana, a true family for the '90s. They're somewhat like the Antrobus clan Thornton Wilder created for his play "The Skin of Our Teeth" in that they take whatever the world, and the writers, throw at them, storm or strife or toxic waste, and somehow survive it. What doesn't kill them makes them stronger.

"This is one of the few shows on television, I think, that rewards you for paying attention," Groening says. "Mostly if you really pay attention to TV you go, 'Oh, this is pretty dumb.' But with 'The Simpsons,' if you pay really close attention, you still can't get everything. There are jokes that, intentionally or not, are only apparent if you freeze-frame your VCR. There are all these computer bulletin boards with long notes the day after an episode: 'Freeze your episode at about 17 minutes in and you'll see such-and-such.' "

Few people will know that Gabbo, the evil dummy who clobbers Krusty on tonight's season finale, is named after "The Great Gabbo," a 1929 movie in which Erich von Stroheim played a deranged ventriloquist. But the writers took the trouble to put that in there anyway.

Twelve writers take turns writing the show. They all get together for planning sessions in a dilapidated conference room near Groening's office. "Don't even inhale," he warns as he opens the door. "The messiest writers' room in Hollywood, we like to think."

The furniture is falling apart, old pizza and doughnut boxes lie about, paint peels from the walls. Groening seems more at home here than in his office. Of course -- it's like being back in college. Or high school. Or ...

"I didn't think I was like Bart at all as a kid," Groening says. "The thing is, I got in trouble for stuff that these days I think a teacher would be delighted by, stuff that was not considered proper use of my time, but it was creative -- cartoons and puppet shows and things like that.

"I can't believe how much of that was discouraged, how much time was spent just keeping kids sitting in a straight line. That seemed way too important."

Yes, Matt Groening has kept contact with the child within. And the child within has made millions and millions of dollars. Don't be a fool; stay in school and doodle. Doodle, as if your life depended on it!