Somewhat literally: McDonalds holds a huge stake in Chipotle. Except Chipotle is way healthier and works better than most fast food joints.
McDonalds holds no stake at all in Chipotle. They did a ways back, but spun it off onto its own through an IPO and divested all shares.
I'm not sure I'd describe them as healthy, exactly. They do place a strong emphasis on using good ingedients, but portion sizes are huge -- a chicken burrito is more than 1,000 calories.