After Steve Burns leans toward the camera to ask, "Will you help me?" there's usually a pause, as though he's awaiting a sitcom-style punch line.

He isn't, of course.

He's waiting for a response from his viewers, usually ages 2 to 5, who are probably watching the same episode for the fourth, fifth or sixth time in a week.

The wide-eyed host of "Blue's Clues" speaks to his audience members as if they are in the same room. And on the same page, which, for the most part, they are not. And that's fine. "Blue's Clues" works best when the viewers are a step "ahead" of the game.

"Do you see the next clue?" Steve will ask, looking utterly bewildered. "Behind you!" a chorus of preschoolers across the country will yell, answering him from their couches at home, feeling empowered, engaged, "smart."

The kiddie series that was supposed to be a quiz show for children when it debuted in 1996 is now an innovative and clever interactive series. It reaches 4 million children per week and generates impressive sales of "Blue's Clues" merchandise, including clothes, toys, books, videos, CD-ROMs and even a play-along kit with a "handy-dandy notebook" like the one Steve uses to write down each episode's clues.

"Blue's Clues," in fact, now outdraws well-established shows like "Barney" and "Sesame Street" when counting preschoolers. It's the first time a show outside the Public Broadcasting Service's sheltered orbit has broken through and appealed to parents in such large numbers.

The show, which on Monday kicked off a special four-part look at the power of imagination, has built its audience steadily since debuting on the cable channel Nickelodeon. And it is bracing for an even larger piece of the kids' TV pie now that it's also airing Saturdays on CBS (Nickelodeon and CBS share the same parent company in Viacom), allowing it to reach households that do not have the cable channel.

Although children's TV advocates like Peggy Charren admit that most of what passes today for children's television is still designed primarily to sell stuff to kids who sit staring dumbly at the fires of the TV hearth, educators applaud "Blue's Clues" for its ability to enhance learning and engage children. Charren, the founder of Action for Children's Television, calls the series "wonderfully astute."

Like predecessors "Sesame Street" and "Mister Rogers' Neighborhood," "Blue's Clues" fosters the social, moral and cognitive development of its pint-sized viewers.

Steve and Blue, his impish computer-generated dog, reside in a computer-generated house of simple shapes and primary colors, where Steve tries to figure out which game Blue wants to play, which story Blue wants to hear or what Blue wants to do in the back yard.

The voices of children on the set responding to and laughing at Blue's antics, then calling out to an oblivious Steve the clues' locations encourages young viewers to call out responses, too.

As they find clues, in the form of blue paw prints on objects, Steve draws the clues in a clunky spiral notebook that, like all the props he works with, is computer-generated.

For example, in one episode, Blue, wanting Steve to guess what he preferred to drink with his snack, put his print on a cup, a straw and a cow. The solution: Blue wanted to drink milk, from a cup with a straw. As Steve looks for the clues and performs simple logic exercises _ for example, asking which item doesn't belong in a group of vegetables in which three are green and the fourth is a carrot.

After three clues have been found, Steve sits in the red Thinking Chair and asks for help in figuring out the answer. Then he sings a song that begins with "We just figured out Blue's clues"" and ends with "because we're really smart!"

Steve and Blue also visit other places, and play with other characters like Mr. Salt and Mrs. Pepper, Pail and his Shovel, Slippery Soap, or Tickety, the clock. They play short games, some as simple as recognizing shapes, with the idea that with repeated viewings (the same episode is shown on Nickelodeon five weekdays in a row) even the youngest child will feel a sense of accomplishment by the week's end.

The show's pace and Steve's sweet personality may remind parents of the gentle, long-running PBS show "Mister Rogers," but kids see a huge difference in the way Steve interacts with his young viewers. He's more peer than father figure. Steve might even be more effective in this age of MTV-inspired visualization because he's animated enough to always keep a child's attention.

"One of the knocks on Mister Rogers, at least from this new generation of TV watchers, is that he can be simply too solemn when on the screen," says Eric Poole, a professor at Southern Illinois University who has written extensively about children's television. "For all his nurturing, Mister Rogers always seemed like a parent introducing kids' stuff. On this show, Steve, to them, IS a kid."

"Blue's Clues" was first conceived by Brown Johnson, Nickelodeon's senior vice president in charge of its Nick Jr. preschool block. She teamed producers Angela C. Santomero and Todd Kessler with Tracey Paige Johnson, a cutout page designer.

The three returned with the idea of a mystery game show with a narrative, along with Paige Johnson's suggestion of making all the characters and objects by hand out of preschool materials and scanning them into desktop computers to be animated. (This is what gives the series a quirky homespun air with the show's otherwise high-tech look.)

"Kids come to television with an active mind, wanting to be stimulated," says Brown Johnson. "We wanted to speak their language, we wanted to be interesting, we wanted to be fun."

"Our hope is that when children turn off the set they'll appreciate the textures and colors in the world around them," Paige Johnson says. "The best way to get the attention of this audience is visually. We like to say around here that the smell test of good children's TV is being able to turn down the sound and still follow what's happening."

Part of the show's success stems from using extensive research with both preschool education experts and children themselves (nothing gets on air without children giving a thumbs-up in test screenings), and writing that's not condescending or preachy.

Brown Johnson says that during its tenure the show has become "a little more challenging" in imparting specific lessons, whether it's about friendship or sibling rivalry or cultural awareness.

Last year, actress Marlee Matlin joined Steve for a series of educational segments designed to introduce the basics of sign language. During "mail time," Steve and Blue visit a school for deaf children and are greeted by children using sign language. Afterward, they "skidoo" (move from one world to another, usually via a TV set) into a storybook where they meet Jane and her friend Carly, who is deaf. Jane and Carly tell them a story using sign language.

Over the next four weeks, the show, airing commercial-free, invites preschoolers to explore the power of their imaginations. Each episode airs every weekday for a week, until the next episode begins. In "Imagine Nation," which kicked off the series, Steve, Blue and their next-door neighbor (talking kitten Periwinkle), use their imaginations to see things in new ways _ imagining that there's an igloo in the living room, that Blue is a dinosaur and that the big paper box in the back yard is actually a fort.

A number of the scenes explain that not everyone sees the same thing, as in one of the live-action segments when kids discuss a cloud shape. One child sees it as "a space ship" while another imagines "two eyes of a mummy."

The show, despite its popularity and acclaim, doesn't come without its critics, though. They include those who say television should be off-limits to preschoolers altogether and those who say "Blue's Clues" _ like so many other kids' shows _ is designed primarily with dollar signs in mind.

But Brown Johnson says she's proud of "Blue's Clues"" breakthrough approach, and even the show's merchandising, "because it, too, follows a certain educational curriculum. ... The toys support the curriculum. We don't do anything without asking, `How can they learn from this?' "

Steve Burns will be leaving the show late next year (his replacement will be named Joe and will be introduced to viewers as Steve's brother). Burns told Reuters news service that the commercial aspect of the show always bothered him and that he was surprised by the degree to which children's television exists to sell toys. (He did add that the creators of "Blue's Clues" were always careful to ensure that content was educational.)

But, says Brown Johnson, "It's also up to the parent to balance commercialism."

The designer Paige Johnson says her own outlook has been influenced by motherhood. Her child is 5 months old.

"It's funny. I used to attack everything as a children's TV producer," Paige Johnson said. "Now it's as a parent. So my feelings toward the integrity of this show are deeper because I'm already at the point of saying it's not if my child will watch 'Blue's Clues,' it's when. And I feel good about that decision."