Want to know why you can't get a McFlurry? So do the feds.

McDonald's ice cream desserts are famed not just for their taste but also for their scarcity. The machines used to make the elusive McFlurry are on the blink enough to have prompted internet memes, social media angst and even conspiracy theories.

One Twitter wag described the disappointment of not being able to order a McFlurry a "universal American experience," along with learning to play the recorder. Even McDonald's has gotten in on the fun: "We have a joke about our soft serve machine but we're worried it won't work," the company tweeted last fall. Then there's  McBroken, a website that tracks the status of ice cream machine at every McDonald's location in America. It shows that 30% of McFlurry makers in New York City are currently on the fritz, while patrons in Houston and Dallas can expect 20%, and 15%, respectively, of machines to be down.