McDonald's has replied to the incorruptible Happy Meal experiment. Somewhere, a team of clown black ops are getting ready to kill us all. The short answer: Our burgers get mold too—under the right humidity conditions! The long answer:
It's hard to believe that a burger sitting on a living room in New York for six months can get mummified, like McDonald's is implying. Even with the A/C unit on, the humidity in NYC is extremely high, especially during the summer months.
To be fair, the correct scientific test would have been to place a fried steak on a plate next to the burger. However, I have the feeling that the steak would have decomposed in a just few days.