Whether or not you like Dunkin', it's hard to argue with this chain's success. Besides being America's oldest donut chain, it's now one of only four restaurant chains with 10,000 locations or more.

In the quest for new and surprising menu items, fast food chains like Taco Bell, Wendy’s, and Popeye’s have jumped on two comfort foods—waffles and pretzels—and they’re being served in ways you’d ...