They're cute. They're interactive. They come with adoption papers. And they're flying off store shelves.

Webkinz, small plush animals, are to today's elementary students what Beanie Babies were in the 1990s. But their fans say they're even better.

Webkinz require regular feeding and exercise or they'll end up heading to the doctor's office. They not only live on their young owners' beds and bedroom shelves, they also inhabit a virtual online world where they can chat with other Webkinz, decorate their personalized rooms and play games.

The toys sell for about $10, with a smaller version, Lil'Kinz costing a couple of dollars less. They're manufactured by Ganz, which apparently was caught off guard when sales started soaring around Christmas. For now, at least, it appears demand far exceeds supply.

"Webkinz Sold Out" reads a sign on the door to Half Off Cards in Londonderry. That was bad news for Sydney Lebourveau, 10, and her sister Rylee, 8, when they visited the store Thursday.

The girls, who already have "adopted" 10 Webkinz and Lil'Kinz, were hoping to add a cow and bunny to their pet family. But they were out of luck, a story that's being repeated around the area on a daily basis.

"The company was obviously not ready for the demand," said Laurie Lebourveau, the girls' mother. "Everyone seems to be out around here."

Brigitte Lopez, a Half Off Cards employee, said the store sold out of Webkinz a week ago and has a waiting list of about 25 people. She said the store has been getting at least 20 inquiries a day about the plush animals and is hoping to get another shipment in soon. Until then, the sign will remain on the door.

Sydney and Rylee will still have plenty to do - tending to the 10 Webkinz already in their personal menagerie.

The toys come with access codes to Webkinz World, an online community where a virtual version of the pet lives. Once registered, children can print off adoption certificates and play games for Kinzcash, used to buy virtual pet food, toys and furniture. Children must care for their virtual pets, and are notified when the animal is hungry, sad or needs to go to the veterinarian.

Kailey Iturrondo, 10, and her brother Brayden, 8, of Methuen have nine of the toy pets between them. They said having Webkinz has helped them learn how to better care for real animals.

"I want to be a vet, and you learn how to take care of different animals," Kailey said. "They all have special food."

That can be a lot to keep track of, particularly for pet owners with ever-expanding collections.

Sarah Sullivan, 6, of Methuen pounced when she spotted the gold-and-black Webkinz leopard on the shelf at Kay's Hallmark in North Andover yesterday.

But after rooting through the 20 different choices, Sarah settled on the floppy-eared basset hound. That choice brought her Webkinz collection to 15. She earned her newest Webkinz after an earlier visit to the dentist.

"Sarah can find any reason for us to buy her a Webkinz," said her mother, Rene Sullivan. "I'm sure she's the biggest collector in the Merrimack Valley, at least the most enthusiastic."

Joanne Rikeman, a clerk at Kay's Hallmark, said the fad has been driving her and other clerks a little crazy.

"We had one woman drive all the way up from the Cape to get a specific one," Rikeman said. "We get calls all the time, asking what we have in stock. If we're not too busy, we call around to our other stores for them."

Even Sarah's grandmother, Patricia LaPointe, has been bitten by the Webkinz bug.

"She calls after she thinks the kids are in bed to make sure she can log on," Rene Sullivan said. "Then she uses Sarah's password to go on the Webkinz Web site, and plays with the pets and see what she can win for her."

Phil Derosa, owner of Country Cupboard in Derry, said the interaction between parents and children puts Webkinz "miles ahead" of Beanie Babies.

"The parents sit down with their children and have to help them get started on the Web site," Derosa said. "I have a background in education, and that's mainly why I took Webkinz on. These are educational tools. Beanie Babies didn't do anything."

He said most customers are children under 12, but not all.

"We got in the Love Puppy, which was put out for Valentine's Day," Derosa said. "We ordered about three dozen and sold out in three days. We called to get more and they said we couldn't get any. They went that fast."

Many other shop owners have complained about not being able to keep up with the demand.

Neil Fineman, owner of Cara's Hallmark in Pelham, said he sold out of Webkinz early in the week and was told the company was at least two months behind on orders.

"They told me that any order placed today would take between 60 and 90 days," Fineman said.

Mary Comei of Annie's Hallmark in Salem said her distributor told her shipments will start to "get better in May."

"We get between 40 and 50 calls a day for Webkinz," Comei said.

Ganz communications manager Susan McVeigh said the company is staying "very focused on supplying retailers" right now, but that things have definitely been "hectic" since the toy's popularity soared.

Joyce Thompson credits the toy with keeping her Little Shop on the Corner in Atkinson afloat.

"The shop flooded in 2006 and there was a lot of major construction going on," Thompson said. "It's hard to stay alive as a gift shop, but (Webkinz) have brought in a lot of new people."

She said it's not uncommon to see children come in with rolls of dimes and allowance savings to buy their own toys.

Megan Mahan, 7, of North Andover did just that.

She and her mother, Shelli, were at Cape Cod Crafters in Salem yesterday, where Megan spent her allowance on a gray-and-white cat, her first Webkinz.

"We can name her after Duffy," her mother said, referring to a cat they lost.

Shelli Mahan said she was eager to sit down with her daughter and figure out the Webkinz World together.

"It's a safe way for her to be on the Internet through me," she said. "I like that these are more than just stuffed animals."

Fun facts

* Webkinz retail for an average of $10, Lil'Kinz for $8.

* Webkinz are 81/2 inches, Lil'Kinz 61/2inches

* Webkinz models now number more than 40, and include cows, pigs, polar bears, poodles and horses.

* Lil'Kinz now number more than two dozen, many of them smaller versions of Webkinz.

* Adoptive owners pick the pet's name and gender.

* Each toy comes with a secret code, which allows the owner to access Webkinz World.

* Don't lose your pet's secret code - it can't be replaced if you do.