From The Daily What:
Three years ago, Redditor atopiary got bored and decided to put the old “McDonald’s fries don’t mold” maxim to the test. Two jars were placed side by side — one containing fries from McDonald’s, the other from KFC — and left unopeded to this day.
As was pointed out, this experiment is by no means scientific, as it doesn’t account for culinary and environmental factors which may have contributed to the preservation of Mickey D’s chips (for instance, higher cooking temps may have killed off most bacteria).
“Agreed,” says atopiary. “It was fun though. Plus it creeps out anyone who looks in the window sill.”