(FORTUNE Magazine) – For years Halloween, a $2.5 billion holiday, had spooked Frito-Lay. With the nation's children fixated on candy, sales of Fritos, Cheetos, and other munchies sank each October. Frito-Lay, though, turned it around by engaging in, as they say in management-ese, "coopetition." Translation: getting your competitor to help you. The company cut a deal with Hershey to market its chips alongside candy. (Get 50% off Cheetos when you buy Hershey bars.) In return, Hershey gets to make use of Fritos' valuable display space in supermarkets. The result: a 15% compound annual growth rate in October snack sales over the past four years. Frito keeps thinking outside the box: This Halloween it's using the popular Goosebumps children's books to help peddle chips as a candy substitute. Trick or chips?