Many childhood memories include hours spent molding Play-Doh, or watching a Slinky glide down the stairs, or marveling at the transfer of a newspaper comic to a simple wad of Silly Putty. But those famous novelty toys didn't start out as products intended for kids.

Failed experiments, re-imaginations and unexpected inspirations are behind the story of seven of America's most beloved toys—all of which have continued to see stellar sales decades after first hitting the market.

What It is: A stretchy pink glob that comes in a plastic egg

Who invented it: General Electric engineer James Wright, who was trying to replicate rubber

The backstory: Wright accidentally discovered the compound for Silly Putty in 1943, when he was working on a World War II-era U.S. government project to discover a rubber substitute. His mix of boric acid with silicone didn't work for that purpose, but the resulting putty caught the interest of a toy store owner, who saw playful possibilities in the fact that it was bouncy, stretchy and moldable. After marketer Peter Hodgson brought the invention to the masses in 1950, it became a hit, and Crayola acquired the brand in 1977. Silly Putty now has a spot in the permanent collections of the Smithsonian National Museum of American History.

WATCH: Full episodes of 'The Toys That Built America' online.

What it is: A brightly colored plastic hoop designed to be twirled around the waist

Who invented it: Arthur "Spud" Melin, co-founder of novelty toy company Wham-O, patented his iteration of a centuries-old idea in 1958

The backstory: In one of the most meteoric launches in toy history, the Hula Hoop sold an estimated 25 million units within just four months of its 1958 debut. Melin and his partner William Knerr didn't exactly invent the idea. Hoop toys date back at least as far as the ancient Greeks. (Think workout gear for the robe and sandal set.) And for centuries, children worldwide found entertainment spinning simple wooden hoops by hand or stick. Nineteenth-century British sailors are credited with marrying the idea of "hooping" with "hula" after encountering Hawaiian dancers in their travels. But it was the sight of an Australian version that inspired Melin and Knerr to manufacture and market the Hula Hoop. Their timing couldn't have been better, since the ascendancy of rock 'n' roll—and Elvis Presley's infamous hips—were inspiring youth to want to gyrate their own. (For its part, the Soviet Union banned the toy as a symbol of “the indecency of American culture.”) But success was hard to sustain: After selling an estimated 100 million Hula Hoops in the first year, the market was saturated. Sales picked back up somewhat with the advent of new versions, including one featuring ball bearings inside that made a “whoosh” sound.

READ MORE: Barbie Through the Ages

What it is: A high-power water gun that claimed to be able to shoot water up to 50 feet away

Who invented it: Nuclear engineer and part-time inventor Lonnie Johnson, who had an accident with a heat pump

The backstory: Johnson was working as a spacecraft systems engineer on the Galileo mission to Jupiter in 1982 when an accident prompted an epiphany: After a prototype for a heat pump sprang a leak, shooting a blast of water across the room, he immediately saw the squirt gun potential. Johnson, a Tuskegee University graduate and U.S. Air Force veteran who holds more than 120 patents, went on to harness that air pressure via an arm-pumping action to create a high-velocity water gun that far outperformed any other on the toy market. After he pitched his idea to the Larami Corporation, the toy debuted in 1990, first as the Power Drencher. A year later, the water gun was rebranded as the Super Soaker, became the top-selling toy of 1992 and went on to do more than $1 billion in sales.

What it is: A molding toy that feels like a cross between clay and bread dough

Who invented it: Kutol Products, an industrial cleaning product company

The backstory: As gas, oil and electric heating replaced coal in American homes after WWII, Cincinnati-based Kutol Products was quickly losing market for its non-toxic clay-like compound used to clean sooty coal dust off of wallpaper. Enter the owner's sister-in-law, who tested the smushy, pliable stuff with her nursery school class as a molding toy—and Play-Doh was born. More than $3 billion of the yellow cans have sold since Play-Doh's 1956 launch, with plugs from TV entertainer Captain Kangaroo helping goose interest early on, and the 1960 introduction of the Play-Doh Fun Factory, which allowed the mush to be pressed into specific shapes, further boosting sales. After changing hands multiple times, Play-Doh was bought by Hasbro in 1991.

What it is: A bouncy spring coil famous for "walking" downward

Who invented it: Mechanical engineer Richard James, trying to improve the stability of WWII naval ships

The backstory: Many Americans may remember the jingle, "A spring, a spring, a marvelous thing, everyone knows it's Slinky!" But they may not know that the bouncy toy coil, famous for tumbling end over end, was the accidental invention of a mechanical engineer who was attempting to come up with an instrument to stabilize naval ships during World War II. Richard James’s 80-foot-long, wire spring coil idea didn't work, but the fact that the sleek and sinuous helical spring could "walk" down pretty much anything made him think it would make a great plaything. Sales started slow, but when a Philadelphia Gimbel's department store agreed to a demo in 1945, all 400 units sold within 90 minutes and the Slinky toy took off. Through the years, it has been put to some creative alternate uses: It served as a makeshift antenna for radio soldiers during the Vietnam War and was highlighted during a 1985 Discovery Space Shuttle telecast to show how it worked in zero gravity. ("It just sort of droops," astronaut Margaret Rhea Seddon said.)

READ MORE: 10 Holiday Toys Through the Decade

What it is: A building toy comprised of interlocking wooden logs

Who invented it: Architect John Lloyd Wright, cribbing from a design of his famous dad, Frank Lloyd Wright

The backstory: Architect Frank Lloyd Wright may have designed innovative structures like Fallingwater and the Guggenheim Museum, but his son, John Lloyd Wright, also an architect, gave the world Lincoln Logs. The notched miniature toy building logs were first produced between 1916 and 1917, inspired by the elder Wright's earthquake-proof design of Tokyo's Imperial Hotel, a project son John assisted on. Packaging featured a picture of Abraham Lincoln with the slogan "Interesting playthings typifying the spirit of America." The set included instructions to build the president’s boyhood cabin as well as the fictional Uncle Tom’s Cabin.

What it is: A pool ball-shaped, DIY fortune-telling tool

Who invented it: Albert Carter, son of—what else?—a Cincinnati clairvoyant

The backstory: Inventor Albert Carter based his early 1944 Syco-Seer prototype on a message board his clairvoyant mother used with clients. It used the basic concept of today's Magic 8 Ball—a sort of crystal ball that housed dice in murky, viscous liquid. (Carter used molasses, writes Tim Walsh, author of Timeless Toys: Classic Toys and the Playmakers Who Created Them.) Carter applied for a patent for his “Liquid Filled Dice Agitator” in 1944, but didn't live to see it granted in 1948. Nor was he there when sales really began to take off in 1950 after a company called Brunswick Billiards asked Carter's company, Alabe Crafts, to rework it to look like a pool eight ball with a 20-sided die. The toy ultimately went on to be bought by Mattel, which claims to sell a million eight balls a year. One note of warning: Should you ask whether you can stash your Magic 8 Ball in your carry-on bag, TSA's answer is "My sources say no."