If you're a fan of Chipotle, you have McDonald's to thank. The burger joint had a large stake in the company, and its investment in the Mexican fast food chain is widely considered responsible for Chipotle's growth. Per Bloomberg, McDonald's had invested around $340 million in Chipotle from its initial investment to when it went public, and when it sold its shares, it profited. However, had it stayed invested in Chipotle, McDonald's could've made much, much more money than it made from the sale. The public was particularly critical of McDonald's in the mid-2010s, and at that time, Chipotle's sales were up, while its former investor's sales were down. McDonald's made every attempt to regain its popularity, including rebranding and major personnel changes, and it's clearly still in business today. If you're looking to have your own stake in either business, Investment U names both companies in the top six fast food restaurants to buy stock in this year.