Jeff Walters, the Beijing-based managing director at the Boston Consulting Group, said that while cross-marketing with games can succeed in bringing in some diners, McDonald's needs to do more to regain trust.

"Getting customers back into the store is quite positive for them in the near term," Walters said. "Keeping them coming back in the long term will require consistently delighting them with the menu and promotions, as well as maintaining a positive food safety record."

McDonald's has taken steps including appointing a food safety chief for China and promising more surprise checks on suppliers as customers avoided its stores in the aftermath of the supplier scandal involving Shanghai Husi Food Co, a unit of OSI Group LLC.

Company executives predicted it would take as much as nine months for sales to recover.

For the Warcraft campaign, three Chinese outlets - in Beijing, Shanghai and Guangzhou - were decorated with wallpaper depicting scenes from World of Warcraft, while animation from the online game play on television screens.

On one weekend, enthusiasts were dressed up as characters from the game, including a lighting god in golden armor and white-haired wizards, who mingled with customers.

World of Warcraft had 6.8 million players globally as of June, making it the top subscription-based role-playing game, according to Santa Monica-based video game publisher Activision Blizzard, without breaking down subscribers by country. Beijing-based NetEase Inc has been licensed to operate the game in China since 2009.

China's online games revenue is poised to exceed 100 billion yuan this year and grow 26 percent each year to 2017 as more operators enter the market and introduce new products, industry analyst iResearch forecast in a report in April.

Sales in the country's fast food industry will grow 10 percent this year to 798 billion yuan, according to Euromonitor International. Yum, with outlets including KFC and Pizza Hut, is China's biggest operator with 5 percent market share, followed by McDonald's with 2.6 percent, according to the London-based research firm.

McDonald's wanted to tap the growing online gaming market where "two out of five Chinese are game players," said Shanghai-based Hui, adding the target audience for the chicken set "is very similar" with World of Warcraft's, mainly male students and working adults at ages between 15 and 35.