When did Percy Spencer invent microwave popcorn?

Percy Spencer did not invent microwave popcorn specifically; rather, he is credited with the invention of the microwave oven in the 1940s. The first commercially available microwave popcorn was introduced in the 1980s, well after Spencer's invention. The combination of microwave technology and popcorn became popular as consumers began using microwave ovens for quick and convenient snack preparation.