The unofficial observance takes place Aug. 30.

What walks down stairs, alone or in pairs, and makes a slinkity sound? If you can sing or hum the rest of that earworm-inducing jingle, mark your calendar to celebrate National Slinky Day on Aug. 30.

The Slinky—a ubiquitous toy-box favorite for several generations of kids and adults—was inducted into the National Toy Hall of Fame in 2000 and made Time’s list of the All-TIME 100 Greatest Toys in 2011. It was invented in 1943 by Richard T. James, a Penn State University graduate and U.S. Navy engineer. According to the Hall of Fame, James was designing springs to stabilize naval equipment. He knocked a spring off his desk and watched it move across the floor, almost as though it were walking. He and his wife, Betty, decided to turn the spring into a toy. She came up with the name and later ran the business. And the rest, as they say, is history.

Seventy-five years after its invention, the Slinky is still available in the original metal coil design as well as giant, plastic and 14-karat-gold-plated ($153.99) versions. Slinky Dog remains popular, too, after its notable appearance in the Toy Story movies.

Random Slinky facts from Alex Brands, which produces the toys in Hollidaysburg, Pennsylvania:

• Sales initially were slow, but after the couple held a Slinky demonstration at Gimbels department store in Philadelphia in November 1945, they sold 400 in 90 minutes for $1 each.

• Slinkys were utilized as mobile radio antennas during the Vietnam War.

• It is the Official State Toy of Pennsylvania.

• Each Slinky contains 80 feet of wire.

• NASA has taken the toy into space for zero-gravity experiments.

• That catchy Slinky song is the longest-running ad jingle ever.