Animation, it's not just for breakfast time anymore. Or for children.

Fox's frisky new "King of the Hill," which so far has held the audience handed it by "The Simpsons" on Sundays, is proving that there is a prime-time audience for more animation.

Sure, we've seen this writing on the wall a few times before. Remember "Capitol Critters" and "Fish Police"? They portended a 1992 animation revival -- which lasted from January to March.

Also promising was "The Critic" in January 1994. The lampoons hit the funny bone more often than they reached a widespread audience on ABC or Fox (following the "The Simpsons," now network television's longest-running prime-time animated series.)

This time -- heh, heh -- it might be different. Fresh off boffo box-office for "Beavis and Butt-head Do America," animator Mike Judge (with "Simpsons" co-executive producer Greg Daniels) again has tapped into a national phenomenon. It might even be bigger than the firestorm that accompanied the early days of his adolescent video addicts on MTV.

In short, we like cartoons. At least this month.

"I think it's fair to say {animation} has come back big time," said Abby Terkuhle, executive vice president and creative director for MTV Animation.

Walt Disney long has recognized the money-making opportunities. So has the four-year-old Cartoon Network, which gets one-third of its round-the-clock toon audience from that key 18-to-49 age group.

"Our audience, including myself, grew up on animation," said Terkuhle. "It's a very powerful medium of expression. Animation has the most direct link of the creators' imagination and the screen. . . . We're committed to developing animated programs, and our audience seems to want more."

MTV -- long identified by its animated logo -- has had more than a half-dozen animated programs aimed at its core audience of 18- to 24-year-olds. Following in the creatively drawn steps of "Liquid TV," "Aeon Flux," "Brothers Grunt," "The Head" and "The Maxx" comes "Daria," a spinoff from "Beavis and Butt-head." The cable video network's first animated sitcom is scheduled to air Mondays at 10:30 p.m., starting March 3.

The sardonic "Daria" and the planned MTV variety show "Cartoon Sushi" will join an increasingly crowded field of prime-time animation.

"I think businessmen have sat around and said, Look at Nick . . . Disney . . . Cartoon Network. This seems like a pretty good business, let's try it,' " said Michael Lazzo, senior vice president of programming and production for Cartoon Network.

Animation is expensive and risky, he said, but many television decision-makers are, like the 38-year-old Lazzo, animation fans who grew up watching classic cartoons.

In addition to its airings of classics such as "The Flintstones," "The Bullwinkle Show" and "The Jetsons" -- all debuted in prime time in the '60s -- Cartoon Network has developed several original programs. "Dexter's Laboratory," "Johnny Bravo" and college fave "Space Ghost" have large adult audiences. So does the new "Real Adventures of Jonny Quest," also airing on TNT and TBS.

Nickelodeon's expanded week-night children's lineup -- including the animated "Hey Arnold!" and "Kablam!" -- has bested the broadcast networks for young viewers, plus gets a large share of those over 18. Adults also make up more than one-fifth of the Saturday evening audience for "Ren & Stimpy" (also an MTV favorite), "Rocko's Modern Life," "Rugrats" and "Aaahh!!! Real Monsters."

The unapologetically rude "Duckman" is still going strong in its fourth season on USA Network. Featuring the voice of Jason Alexander (one of several celebrity actors to help draw older viewers to cartoons), the series got 42 percent of its audience from adults before moving up three hours to 7:30 Saturdays.

Comedy Central's prime-time lineup features the off-the-wall "Dr. Katz, Professional Therapist" as well as encore performances of "The Critic" and Fox's Saturday-morning cult fave "The Tick."

This spring, HBO's new animation division plans to unveil two new adult shows: "Spawn," an adaptation of Todd McFarlane's comic book, and "Spicy City," created by animator Ralph Bakshi.

And Warner Bros., which failed to take over the prime-time (Nielsen) world with the clever "Pinky and the Brain," is set to try again with an animated action-adventure series, "Invasion: America," slated for January 1998.

Eh, what's up, Doc?

"I think you'll see more and more of it," Lazzo said. "Listen, if there are great shows, in the long run it helps everybody. Overall, it makes people feel great about watching animation on television."

But if "King of the Hill" or another broadcast network series doesn't become a hit, television executives might well go back to the drawing board. And even fan Lazzo isn't sure "King" will rule among all age groups -- a key to extended success.

" King of the Hill' will never be able to do that in its current guise," he predicted. "I happen to think it's a very funny show. I wish most live-action sitcoms were as funny. . . . It will be interesting to see, over a period of time, whether kids watch in large numbers."

Funny, isn't it? The newest Golden Age of Adult Animation might depend on the viewership of children. CAPTION: "King of the Hill," with guest Willie Nelson, joins adult-friendly animated shows such as "Beavis and Butt-head" (top), "The Simpsons" and "Duckman" in prime-time schedules.