Like her American cousin Bart Simpson, the popular Japanese cartoon character Chibi Marukochan is out to prove it's OK to be an underachiever.

Her relentless mediocrity has won over a nation obsessed with overachieving, making Chibi an unlikely idol and the year's hottest fad.The lazy third-grader of slurred speech and bob-cut hair even looks a bit like Bart. Both are drawn two-dimensionally, with a minimum of detail and unsure lines.

Chibi's self-proclaimed ambition is to get away with doing the minimum, but her market performance has been phenomenal.

More than 9 million copies of her comic books have been sold, and the spinoff television show has the nation's top rating, with two of every five sets tuned in each Sunday at 6 p.m.

The show's theme song of nonsensical lyrics has sold 1.7 million compact discs and cassette tapes. It is heard endlessly in Japan's countless karaoke bars, where drinkers provide the singing voices to recorded music tracks from popular songs ("Kara" means empty in Japanese; "Oke" means orchestra).

A leading toymaker, the TAKARA Co., figures to make $40 million this year on Chibi Marukochan dolls, badges and games. People have been arrested for selling fake Chibi T-shirts.

Sociologists hold seminars at Waseda University on the Chibi Marukochan phenomenon, and her likeness graced a portable shrine at autumn festival of the Tokyo National University of Fine Arts and Music.

The Chibi frenzy doesn't grab everyone. Chikako Ogura, a well-known psychologist, sees something sinister in it.

"The worshiping of kitsch bourgeois tastes is the underlying force in fascism," he said.

As with "The Simpsons," the story line for "Chibi Marukochan" centers on family and school friends.

Both "are told from the child's point of view," said Kenji Shimizu of the Fuji Television Network programming division, who supervises the cartoon show. "That's why they talk the way real kids talk, not in proper complete sentences like Disney characters. And that's why kids gravitate so much" to Chibi.

Shimizu believes the two anti-heroes "are exactly the same concept, except the cultures they reflect are totally different."

Bart is a rude but ingratiating brat, while Chibi's comments tend to be muttered growls rather than outright statements.

"She is more emotionally sensitive, which I see as a cultural difference," said Hiroyuki Horikomi, agent for Momoko Sakura, Chibi's creator.

Chibi ponders for hours how to spend her $1.60 allowance. She envies the attention lavished on a schoolmate with a bloody nose. A new cordless telephone is a major family event. Cleaning up and homework are tasks to be avoided as long as possible.

Shimizu said the passive Chibi, who fears standing out or being disliked, strikes a responsive chord in children who grow up in a conformist and competitive society.

She also has charmed older Japanese, particularly working women aged 20-25, Horikomi said.

"Chibi Marukochan," set in the early 1970s, jogs childhood memories for those women, who often live with their parents and have money to spend on memorabilia.

The comics and cartoon are sprinkled with details from the 1970s calculated to feed nostalgia, from pop hits to yo-yos to toys in packages of instant noodles.