"Zhu Zhu Pets are everywhere!" -- or so goes their catchy jingle. Come Christmas morning, retailers across the country hope that will be true.
Zhu Zhu Pets, the cuddly, on-the-go hamsters who squeak, roll, even drive their own cars, are on their way to becoming the holiday season's "must-have" toy.
Retailers like Ken Levinsohn, owner of the Learning Express toy store in Scarsdale, N.Y., hope they'll be the hamsters that save Christmas.
"Based on the demand, it's going to be hot," Levinsohn said.
The trouble is for Levinsohn is that he has none to sell. Following in the footsteps of must-haves of seasons past -- the Furby, Tickle-me Elmo, Cabbage Patch dolls, Beanie Babies -- supply seems to grow short just when demand is high, and Zhu Zhu Pets are flying off store shelves.
"It's easier to get a swine flu shot than to get Zhu Zhu Pets," said customer Julie Gerstenblatt.
Levinsohn said he has been waiting for another shipment for nearly two months. "Clearly, the demand is there. The product is not. It's very frustrating," he said.
But it isn't just small independents like Levinsohn who are having trouble getting hold of Zhu Zhu Pets. Even the biggest retailers say they can't get enough.
At the Toys "R" Us in New York City's Times Square, salespeople don't bother putting Zhu Zhu Pets on the shelves. Every shipment has sold out in a matter of hours.
One salesperson told us that even the accessories, which are sold separately from the coveted pets, were running low. At one store, shopper Theresa Brdaric scored the last Zhu Zhu Pet car.
"The cars are going for quite a bit on Ebay. The cars and the ball are the biggest sellers on Ebay, I think. I'm just happy to get some," she said.
On Ebay, the $9 hamsters are being auctioned for up to $60 a piece.
"At the end of the day, you can't predict a fad. Some people will tell you you can but it's not possible. When something really catches the imagination,then you've got people who wouldn't normally buy these toys looking for them," Byrne said.
"I think with the Zhu Zhu Pets -- everybody's been talking technology, cell phones, iPods. This is sort of, even though its great technology, it's the antithesis of that because it's really fun, and creative and it's a classic play pattern," he said.
Last Christmas, with the economy in turmoil, retailers suffered badly. But Zhu Zhu Pets are miraculously bringing people back into toy stores.
"You know, it may be the hamster that saved Christmas because it's a rising tide lifts all boats. It's got people coming to the stores. They're looking to find these. But then they're looking around at other things," Byrne said.
"Nightline" visited the Zhu Zhu headquarters near St. Louis, where the pets' creator, Russ Hornsby, introduced us to his top-selling line of characters. They have names like "Mr. Squiggles," "Chunk," "Num Num," and "Pipsqueak."
Hornsby said they didn't make many of the robotic hamsters at first, because he didn't know if they would catch on.
The response has been "phenomenal ...unbelievable," he said. "I've never seen anything like this in my entire life and probably will never see anything like it again in my life."