The cute, little robotic hamster has a target on its back.

Cepia, the small Clayton-based toymaker behind Zhu Zhu Pets, has been bracing itself for knockoffs since its toy became the runaway hit of the last holiday season. Now Hasbro, the $4 billion heavyweight behind Transformers and Mr. Potato Head, is angling for a piece of Cepia's pie with its new line of lower-priced Furry Frenzies that resemble Zhu Zhu Pets.

And while it has undeniably been a blockbuster success, analysts wonder about Zhu Zhu's momentum. The notoriously faddish toy world is already speculating what the next big thing will be this year to dethrone Zhu Zhu — Squinkies? Sing-A-Ma-Jigs?

Zhu Zhu Pets sold out of stores during the holiday season, but since then, Cepia has caught up to demand and widely distributed them to many retail outlets — from Walmart to Target to drugstores like CVS. Now there have been some signs that the popular toy's frantic pace of sales has begun to slow.

Kansas City-based Hallmark was pleased with the success of its exclusive Zhu Zhu Fluffy Bunny that was sold only at Hallmark Gold Crown stores around Easter, said Deidre Mize, a Hallmark spokeswoman. But the company recently marked down the rest of its Zhu Zhu Pets inventory by 40 percent.

"As with all hot toy trends, their appeal can fade fast, especially if there is wide distribution in the market," Mize wrote in an e-mail. "I think I can safely say that we've seen a decline in demand for the product at our corporate owned stores, but can't speak to the majority of our independent store owners."

Overland-based Build-A-Bear Workshop also recently decided to exit the Zhu Zhu line after the rollout of the toys to all of its stores earlier this year did not go as well as expected. So it has also marked down the toys.

Zhu Zhu Pets were so hot last year that alternative channels of distribution like Hallmark and Build-A-Bear initially had success selling them, said Gerrick Johnson, a toy analyst with BMO Capital Markets. The fact that they are now marking them down is a sign that there is a slowdown in the brand, he said.

"Zhu Zhu is falling off the proverbial cliff," Johnson said. "Zhu Zhu Pets is one of the fastest hot toy cycles I've ever seen. … Every retailer has way more Zhu Zhu Pets than I think they need."

But Russ Hornsby, the chief executive of Cepia, said in a statement to the Post-Dispatch that there has been no drop-off in demand. Though he declined to provide figures, Hornsby said global sales continue to rise and that Zhu Zhu has done more in sales this year than it did all of last year. The toys were not widely distributed to retailers until the second half of last year.

"We are anticipating our biggest fall and holiday season ever," Hornsby said. "In fact, we expect our year over year sales increase to be ten-fold."

Two key retailers also voiced support for the brand.

A Target spokeswoman said the retailer beefed up its inventories and selection of the toys earlier this month and plans to sell them through at least spring of next year.

And a Toys R Us spokeswoman wrote in an e-mail that Zhu Zhu Pets continue to be "top sellers." She added that the Zhu Zhu Pets backpack has been especially popular for the back-to-school season.

Sean McGowan, an analyst with Needham & Co., said a hot toy like Tickle-Me Elmo often has a bigger second year after selling out the first year even though it loses the perception of being the hot toy when supply catches up with demand.

"I think the overall sales will be a lot bigger," he said of Zhu Zhu Pets in its second year. "But because it's so much more available, the rate of sale will be lower. They couldn't come close to meeting demand last year. Now I don't see it selling out."

It's not unlike the buzz around a new movie, he added. Movies used to open at a limited number of screens and would sell out, prolonging their shelf life. But now a new movie will open simultaneously at thousands of screens across the country.

"Demand can be met a lot quicker, but that means that sales are going to fall off," he said. Zhu Zhu "is a success story no matter how you look at it. But that doesn't mean it will sell forever."

During the first half of this year, Zhu Zhu Pets have outsold Webkinz, Beanie Babies and Build-A-Bear Workshop as the top-selling property in the "plush" category in the U.S., according to the NPD Group, a research firm based in Port Washington, N.Y. No sales figures were provided by the firm.

Cepia says it will continue to build on the momentum with other innovations. Kung Zhu — Cepia's new line of fighting hamsters aimed at a boy audience — started hitting stores in June and has performed well, Hornsby said. Kung Zhu is the first in a "long line" of new Zhu Zhu Pets it plans to introduce this year and beyond, he said.

But analysts say the jury is still out on whether Kung Zhu will take off.

"Some say it's not going as well as hoped," said John Taylor, managing director of Arcadia Investment Corp. "And some say it's still early to tell."

While Zhu Zhu may not have quite the same momentum as it did last year, Taylor said he thinks it will still be a major player this year.

"They are definitely on a roll," he said. "It's still one of most successful new toys in several years … And nothing attracts competition like success."

Hasbro has obviously taken notice. Its Furry Frenzies line is hitting shelves of mass retailers like Walmart, Toys R Us, Target, and Kmart.

A Hasbro news release describes the new line as "adorable pets with personality that skitter, scatter, bump and go where they want to."

Furry Frenzies are being sold for $7.99 — $2 cheaper than Zhu Zhu Pets.

None of the animals are hamsters. There is a bunny, chipmunk, raccoon, kitten, puppy and a hedgehog. (The Zhu Zhu menagerie has also expanded outside of the hamster family this year into other woodland creatures, including a bunny, a raccoon and a hedgehog.)

"But the rabbit — you snip off his ears and he looks like a hamster," said Johnson. "I think it's pretty blatant."

The toy world is littered with examples of imitations, but it's somewhat new territory for Hasbro, which has been more of an innovator in recent years, Johnson said.

Analysts think Hasbro's muscle and size might give it some more leverage with retailers, but that consumers will still be drawn to the Zhu Zhu brand.

"It's hard to believe they won't have some success taking some share in the segment," Taylor said of Hasbro.

Furry Frenzies' lower price might attract some consumers, McGowan said. And it might force Cepia to lower its prices on Zhu Zhu Pets, he said.

"But I think generally consumers want the real brand," McGowan said. "Nobody knows the Furry Frenzy line."

In the meantime, the toy world is already abuzz about new toys entering the market such as Sing-A-Ma-Jigs, teddy bears that sing when you press on their bellies, and Squinkies, small, squishy dolls that come packed in a bubble.

"What I think is really blowing the doors off is Squinkies," Johnson said. "That's the new Zhu Zhu Pet."