For those, on the other hand, whose lives require fluency in Rugrats and Catdog, the fact that SpongeBob reels in 2 million children every night is a no-brainer. The show, which debuted on Nickelodeon three years ago and has since gobbled up the children's cable television market, is a loopy half-hour ride that youngsters clearly enjoy. It also has been aggressively marketed. Young fans can strap on SpongeBob backpacks each morning and tuck into SpongeBob sheets every night.

But it's that other part of the audience — the nearly 5 million adults who also tune in every week (and who purchase millions of dollars worth of the merchandise for themselves) — that is elevating SpongeBob from child's confection to cult classic.

Why that should be so isn't entirely obvious. The tenor of "SpongeBob SquarePants" is distinctly sweet and silly. It lacks most of the blatant scatology of recent crossover hits like "Ren & Stimpy," and avoids the acerbic social commentary of adults-only cartoons like "The Simpsons" and "South Park." SpongeBob, in contrast, "lives in a pineapple under the sea" (were you singing along?) with his pet snail, Gary. He is a relentlessly optimistic naf with a sound work ethic and an affinity for tighty-whitey underwear who basically has fun and plays nice. And that in the end, may have been a shrewd — or lucky — stroke, as it seems to have tapped into something that the culture was ripe to consume.

"Virtually every great cartoon, both in the sense of being commercially successful and artistically successful, somehow has a simultaneous appeal to both adults and kids," said Timothy Burke, a professor of history at Swarthmore College and an author of "Saturday Morning Fever: Growing Up With Cartoon Culture" (St. Martins, 1998). "SpongeBob seems to have a different formula for doing that than most of the shows that have pulled off the same trick in recent times."

For most successful cartoons in the last decade or so, that formula has involved giving children fun characters, plot lines that }“µъon't condescend, and knowing winks to the adults in the audience. Popular shows like "The PowerPuff Girls," Professor Burke says, do this extremely well. "They'll have giant monsters destroying a city, and they know there's a portion of their audience that has seen Godzilla movies and knows all the tropes and plot turns associated with Godzilla movies, so they play that for laughs."

Of course, variations on that formula are at least as old as Bugs Bunny and the Warner Bros. cartoons from the 1930's and 40's, which routinely lobbed knowing, often irreverent tidbits over the heads of children and into the laps of adults who recognized — and appreciated — the favor.

SpongeBob is rarely so overt in its subversion. The characters are all somewhat stupid and unaware of themselves. Some are grumpy and mean, but rarely malicious. But that's not to say that the show lacks a barbed wit that is firmly contemporary. There are plenty of subtle scatological riffs and sly references to the banality of middle-American life, for instance. Still, the show ends up evoking a civility that is unusual in modern cartoons.

"There is something kind of unique about this," said Robert Thompson, a professor of communications and director of the Center for the Study of Popular Television at Syracuse University. "It seems to be a refreshing breath from the pre-irony era. There's no sense of the elbow-in-rib, tongue-in-cheek aesthetic that so permeates the rest of American culture — including kids' shows like the `Rugrats.' "

BUT that apparent lack of sardonic self-awareness in a culture defined by wiseguy knowingness may be exactly what works for SpongeBob. Adults — and even kids — know the wink-and-nudge routine all too well. "I think what's subversive about it is it's so incredibly nave — deliberately," said Professor Thompson. "Because there's nothing in it that's trying to be hip or cool or anything else, hipness can be grafted onto it."

Not surprisingly, SpongeBob's creator, Stephen Hillenburg, says he's simply trying to make people laugh. He drew inspiration, he says, from Charlie Chaplin, and from Peewee Herman — both of whom made naivetй the core of their comedy. He also mentions Laurel and Hardy. "Stan was always like this kid with this innocent view, and there's always a certain amount of comedy that you can derive from that in a setting where other characters are a little more jaded."

Mr. Hillenburg is also careful to point out that SpongeBob is a product of many creative minds coming together with a simple mission: fun. "We try to write the show to make ourselves laugh," he said. "And we're not thinking about how to analyze it afterward or how it fits into the pop culture now. It's really just a matter of what do we think is creative and hopefully funny."

So far so good — and the imitators are surely on their way.

"Every time something like this succeeds TV executives have meetings and they sit around tables and they try to figure out why it succeeded," Professor Burke said, "and they invariably miss the point: That it succeeded because you gave some good creative people the freedom to make something creative. Instead, they sort of boil it down to a list of things and say `well, do more of that.' "