Once upon a time, the relationship between children and their stuffed animals was driven solely by youthful imagination.

But now, Build-A-Bear Workshop has developed a virtual world found at www.buildabearville.com, where children and their furry friends can come to life together. They can go on adventures, play games and make new friends.

They might run into "High School Musical" star Lucas Grabeel, whose online character will be in www.buildabearville.com through April 9. Even Maxine Clark, chief executive, appeared in the virtual world in the form of a girl bear on her birthday earlier this month.

The Overland, Mo.-based company says it's the only children's retailer to have its own virtual world that has connections to Build-A-Bear's bricks-and-mortar stores. While this may be a new step for a retailer, the creation of virtual worlds has been a growing trend among toy makers, said Alison Marek, managing editor of TDmonthly Magazine, a Los Angeles-based trade magazine for the toy industry.

"You practically can't launch a toy anymore without a corresponding Web site," she said.

She said the trend took off when toy maker Ganz introduced its popular Webkinz plush creatures in 2005 along with a Web site, www.webkinz.com. The site allows children to build virtual worlds for their toys using an identification code that comes with each Webkinz animal.

In August, The Walt Disney Co. bought Club Penguin, a subscription online virtual world at www.clubpenguin.com that allows children to play with animated penguins inhabiting a snow-covered virtual world, chat with other users and furnish a virtual home with currency earned inside the game. The fee is $5.95 a month or $57.95 a year.

A Disney spokeswoman said Club Penguin is not associated with Disney Stores. However, Club Penguin does sell merchandise related to the virtual world online.

Build-A-Bear has added a twist to the concept by linking the virtual world to its real stores, where children make their own stuffed animals and select clothing and accessories.

"The strength of our brand is customization, personalization and high touch. These translate into the virtual space very well," said Dave Finnegan, chief information officer. "It's like paper dolls in 3-D."

More than 1.5 million "guests" have registered to use the site since it was launched in December. Sometimes parents take the step for their kids. Among them is Rachel Edmiston, a Paragould, Ark., mother who said she signed up her two daughters, ages 14 and 11.

Edmiston found the site appealing because it would help her daughters improve their computer skills and at the same time learn fundamentals about earning and spending money. Children can earn "money" by playing games, and they can buy items from the "virtual" stores and trade those items among themselves.

"It's helping them learn about how to use money wisely," she said. "They are even learning how depreciation works."

The site's safety features aimed at protecting young participants are also impressive, she said.

For example, before a child's registration can be activated to play in www.buildabearville.com, parents receive an e-mail asking them to choose a communication option based on age. Children younger than 12 are limited in their virtual world chats to "prebuilt" phrases, said Greg Hammond, Build-A-Bear's director of interactive services. Older children can participate in "safe, open chat," that is limited by a "safe dictionary" of words.

Build-A-Bear programmers keep refining that dictionary as kids find ways to get around limitations, Hammond said. For example the company had to remove the word "beach" because of the context in which older children were using it.

This virtual world also doesn't allow children to type numbers, so no personal information like phone numbers or addresses can be exchanged.

Once parental permission is given, a child can play in www.buildabearville.com without owning a Build-A-Bear toy or paying a subscription fee. However, a child does need to own a Build-A-Bear creature to bring a furry friend to life and to decorate a home, called a Cub Condo.

"We felt there was more of an advantage to let you in and see what the site is about before making a purchase," Hammond said. "We see it as the ultimate gift with purchase."

"Birth certificates" issued with stuffed animals made since October include a code that allows children to register their toys in the virtual world and create a corresponding animated version. If they have creatures made before that time, they can get a code by visiting a Build-A-Bear store.

Without the code, a child can still create an avatar, an online graphic representation of themselves, to play in the virtual world. They can choose hair and skin color and clothing for the avatar, visit about 25 different areas, chat with and trade virtual goods with other participants and earn virtual money.

However, upcoming enhancements and promotions will make visiting a physical Build-A-Bear store and owning a real Build-A-Bear friend more attractive.

For example, programmers are giving animated furry friends additional capabilities so they can interact with a child's avatar.

"Not only will they greet you," Hammond said, "but they'll even clean your condo."