Isaac Larian, the founder and CEO of toymaker MGA Entertainment, is an insomniac. Fortunately for him, that inability to sleep forced him to get up out of bed one night—a move that ended up being worth $4 billion.

Larian’s company is the architect of L.O.L. Surprise!, a line of dolls with a clever conceit. The product, which retails for about $10 to $20, is encased in a ball-shaped plastic shell and buried under layers of packaging, forcing children to tear through a gauntlet of wrapping before they’re able to see it. The inspiration came on that highly profitable sleepless night, which Larian spent watching unboxing videos on YouTube. It resulted in the first toy made for a generation wired for delayed gratification.

The dolls first went on sale in test markets at select Target stores in late 2016. MGA shipped out 500,000 of them, all of which sold out within two months. A Cabbage Patch Kid-esque frenzy came the following year. By late 2018, L.O.L. Surprise! (the acronym stands for the fancifully redundant Little Outrageous Little) had moved 800 million units, accounted for seven of the top 10 toys sold in the U.S., and was named Toy of the Year by the Toy Association. Videos of kids and adults unboxing them garner millions of views on YouTube, which is precisely where Larian knew his marketing would be most effective.

Cindy Ord, Getty Images for MGA Entertainment

The dolls themselves are nothing revolutionary. Once freed from their plastic prisons, they stare at their owner with doe-eyed expressions. Some “tinkle,” while others change color in water. They can be dressed in accessories found in the balls or paired with tiny pets (which also must be "unboxed"). Larger bundles, like last year’s $89.99 L.O.L. Bigger Surprise! capsule, feature a plethora of items, each individually wrapped. It took a writer from The New York Times 59 minutes to uncover everything inside.

This methodical excavation is what makes L.O.L. Surprise! so appealing to its pint-sized target audience. Though MGA was advised that kids wouldn’t want to buy something they couldn’t see, Larian and his executives had an instinctual understanding of what child development experts already knew: Kids like looking forward to things.

Dr. Rachel Barr, director of Georgetown University’s Early Learning Project, told The Atlantic that unboxing videos tickle the part of a child’s brain that enjoys anticipation. By age 4 or 5, they have a concept of “the future,” or events that will unfold somewhere other than the present. However, Barr said, they’re also wary of being scared by an unforeseen outcome. In an unboxing video, they know the payoff will be positive and not, say, a live tarantula.

L.O.L. Surprise! is engineered to prolong that anticipatory joy, with kids peeling away wrapping like an onion for up to 20 minutes at a time. The effect is not entirely novel—baseball card collectors have been buying and unwrapping card packs without knowing exactly what’s inside for decades—but paired with social media, MGA was able to strike oil. The dolls now have 350 licensees making everything from bed sheets to apparel. Collectors—or their parents—can buy a $199.99 doll house. So-called “boy toys” are now lurking inside the wrappers, with one, the mohawk-sporting Punk Boi, causing a mild stir for being what MGA calls “anatomically correct.” His tiny plastic genital area facilitates a peeing function.

Whether L.O.L. Surprise! bucks conventional toy trends and continues its popularity beyond a handful of holiday seasons remains to be seen. Already, MGA is pushing alternative products like Poopsie Slime Surprise, a unicorn that can be fed glitter and poops a viscous green slime. An official unboxing video has been viewed 4.2 million times and counting.