Those are fake, those pictures were posted by netizen PS, and those chickens are Israeli hairless chickens, not KFC chickens. Let you have a look at KFC's article:

The rumor of KFC's "strange chicken" broke down.

A few years ago, there were rumors about KFC's "multi-winged strange chicken", accompanied by absurd pictures of PS synthesis. In this regard, KFC quickly stated that KFC attaches great importance to food safety, and all the chicken raw materials used are from domestic suppliers with a certain scale and good reputation. The rumors circulating on the Internet have no scientific basis.

After that, the rumor was almost forgotten by everyone, but after entering 2008, the rumor of KFC's "strange chicken" reappeared on various websites and forums, and was reprinted by netizens. The compiled content and pictures are even worse, confusing the audience and causing trouble to some consumers. Due to the imagination of posting users, superb photo PS skills and certain influence on society, this incident was counted as "eight outrageous events in 2008" by the Legal Evening News, and the rumor of KFC's strange chicken was broken.