Naval engineer Richard James was having a terrible day in 1943. While working on springs designed to stabilize sensitive ship equipment during rough seas, he knocked one off a shelf. Instead of just hitting the floor, the spring "walked" down a stack of books, onto a table, and finally settled on the ground. Most people would've just picked it up and gone back to work. James saw a toy.

He spent the next two years perfecting the tension and specs of his metal coil, trying out different materials until he found the perfect "walk." His wife Betty came up with the name after thumbing through a dictionary and finding "slinky," which means sleek and graceful. In 1945, they borrowed $500 to manufacture 400 units, unsure if anyone would actually buy a walking spring. Their first demonstration at Gimbels department store in Philadelphia sold out in 90 minutes.

Here's the wild part: Richard eventually abandoned his family and the company in 1960 to join a religious cult in Bolivia. Betty took over and turned Slinky into an empire, running the company for nearly 40 years. She simplified production, slashed the price, and made it an American icon. Over 300 million Slinkys have been sold worldwide, and if you stretched them all end-to-end, they'd wrap around the Earth more than 150 times. Not bad for a dropped spring.