McDonald's McRib sandwich is a unique combination of exclusivity, scarcity and seasonality that has made it a cult favorite. The sandwich is made with certain pork trimmings, and when the price of those trimmings rises, McDonald's takes the McRib off the menu. It was first introduced in 1981 and has been making regular appearances since then, usually around November. The McRib has been featured in an episode of The Simpsons and has a devoted fan base, but it's unlikely to ever become a permanent menu item.
McDonald's brings it back for a limited time each year to increase sales in its fourth financial quarter. The McRib is not actually a rib, but rather a molded burger made with pork ingredients and flavors. It's a limited-time menu item that returns based on consumer demand.