News that Rovio Entertainment Ltd., creator of the hyper-popular Angry Birds game, is planning to open its own retail outlets in China next year comes as little surprise to the vendors in the country's markets. The bigger question might be why they waited so long to cash in on their popularity.

Among the aisles of cut-rate and knockoff cellphones, digital cameras and other gear, sales of largely unauthorized Angry Birds merchandise have been flourishing for months. Themed iPad 2 covers and USB memory sticks abound, as do cheap plastic watches, T-shirts, balloons, buzzing battery-operated birds and plush stuffed toys – some dead ringers for the real thing, and some renditions that would no doubt make the game's creators grimace.

"They are very popular. They go with iPhone 4 and iPad and what's more popular than iPhone and iPad?" said Hua Li, 22, a vendor in the city's Silk Market whose wares included the iPad covers, but whose stash of USB sticks had run out. "If they opened a big shop full of this stuff, they would have a lot of customers."

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This week Angry Birds became the most downloaded game of all time, reaching 500 million downloads. Around 50 million of those downloads have been from China, where Apple's sales of iPhones and iPads, the first platforms for playing the game, are also growing at record pace.

Earlier this year a theme park in the city of Changsha even created a live version of the game, allowing players to catapult stuffed Angry Birds at green pig balloons – albeit without the permission of Rovio.

At a TechCrunch conference in Beijing this week, Rovio's chief marketing officer Peter Vesterbacka told journalists that Angry Birds was "the most copied brand in China" and said the company would soon open retail shops in the country. To illustrate his point, he wore an Angry Birds T-shirt and carried some unauthorized Angry Birds balloons.

The company already sells Angry Birds gear through an online store and is about to open a retail store in Finland, its home base.

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"Clearly there's a lot of demand for it – the game and physical products. We want to sell officially licensed and good quality products, but at the same time we have to be happy that the brand is so loved," he said, quoted by trade publication MCV. Rovio opened its first office in China, in Shanghai, last month.