Once upon a time, Tinkerbell was known as the magical fairy who helped children fly. Now Disney is summoning the mischievous little sprite from Peter Pan to get kids to go online.

In a new virtual world called Disney Fairies Pixie Hollow, girls and boys can become a fairy, dress up, fly around, befriend other fairies and help paint lady bugs, teach baby birds to fly or go on other nature-related quests. It’s packaged as the world of Tinkerbell and her friends, and their work is to make nature happen.

More children’s toys are incorporating an online component, extending the world of imagination from sand boxes and toy boxes to the computer screen, blurring the distinction on the way. Seeing the success of Webkinz (the stuffed animal that comes alive online in Webkinz World), big-name companies and unheard-of startups alike are tapping into their own imaginations to try to develop unique interactive sites for kids. It’s a tight race to produce the most compelling place for the already over-scheduled kids they’re trying to attract.

And for parents, the games can present new challenges as they wonder what stimulates kids’ creativity, and what may stifle it, or whether some games focus too much on consumption.

But toy makers often emphasize the real-world skills or socialization the games may encourage.

Disney’s new virtual world, which the company says will launch sometime this year, will be an extension of the already existing site www.disneyfairies.com, where kids can create, dress up and decorate fairy avatars.

When the Pixie Hollow site goes live, it will be accompanied by a line of real-life toys called Clickables. Created by Hong Kong-based toy company Techno Source, they are bracelets and charms with tiny computer chips built in that share bits of information when pressed to each other. If a girl has a bracelet, which will sell for $19.99, she can click it to a friend’s bracelet, and then their fairy avatars will be friends in the online world of Pixie Hollow.

“No longer will you be passively watching these famous fairies, who you’ve always had this distant, passive relationship with,” says Steve Parkis, senior vice president for Disney Online. “You’ll be interacting with them.”

Other games are more solitary.

A New York-based startup called Intellitoys sells a stuffed animal called smart-e-bear, which comes with built-in music you can access by squeezing a paw or downloading onto a computer using an Apple iTunes-like program.

For the young sci-fi fan, there’s Test Tube Aliens – a toy whose extraterrestrial life you “hatch” in a real-world test tube, and whose age, health and sleep you monitor online at www.testtubealiens.com.

Some sites focus on good conduct.

A new site aimed at parents and kids assigns rewards (real and virtual) to a chore list. Say goodbye to gold-star stickers and hello to new accessories for your kitty avatar!

At www.handipoints.com, parents can program in their own point system alongside a virtual awards system created by the developers. A kid who makes his bed might earn two points toward a new DVD from Mom and a new virtual outfit from the game-makers. The idea is to give you organization and incentive for doing what you should do anyway.

“It’s really just a way for you to make your life easier, not a replacement for the things that you need to be in the off-line world,” says HandiLand CEO Viva Chu.

A recent report for marketers from interFUEL Interactive Design & Technology, based in Ventura, Calif., lists the seven must-have features for any Web site aimed at kids, tweens and teens.

“If your company doesn’t start using this new medium to enrich your brand, your competition will,” the report says.

The seven essential features include safety, fun and self-expression, according to the report.

“If you’re the fat kid at school, you can go online and be the skinniest person ever,” says Mel Bergman, the director of business development at interFUEL, citing a common allure of the Web that applies to all age groups.

But there’s some irony inherent in bridging the online and off-line worlds:

A virtual world tries to entice kids to help nature, but instead may draw youngsters to spend more time on the computer, an energy-consuming device, and less time playing outside. An overweight child, enjoying his virtual liberation as a skinny avatar, does nothing for his actual physical health by sitting motionless in front of a computer screen.

“We’re all working really hard to pay for these electronic things that we think we need,” says child psychologist Stephanie Pratola, in Salem, Va. “But what I know about kids is that it’s their relationships that help them grow and develop. And it’s not a virtual relationship. It’s a real relationship.”

She says kids’ imaginations also get cheated when a fake world is created for them by computer programmers and toy makers instead of letting them loose to make something up themselves.

“It’s like everybody using their imagination in a similar way, which, how imaginative is that?” Pratola says. “There’s really no substitute for a child creating something out of sand or mud or water.”