If you are not a child, don’t have a child, or don’t know anyone with kids, there’s a chance you’ve never heard of a Hatchimal, the must-have toy for Christmas this year.

Allow me to introduce you: the Hatchimal is a plush little robot that comes trapped in a sealed, football-sized plastic egg. As soon as you take it out of its packaging, it comes to life — you can see its eyes glow through the shell, and hear it make cooing sounds. After you warm it up, move it around, and knock on the shell (and it knocks back), the Hatchimal starts to peck its way free with its spring-loaded beak. And then it asks you to play.

With Hatchimals, Spin Master, the Toronto-based company behind the toys, has had a surprise hit. They sold out (at $59.99 MSRP) almost as soon as they reached shelves in October of this year. Smart parents smelled the oncoming craze and snagged one early. Evil geniuses, like the Zappa brothers from Arizona, cashed in on the hype by stockpiling Hatchimals (before stores started limiting sales to one per customer) then reselling them for more than $150 a pop on eBay. Evil un-geniuses, like the woman who wrote *Water for Elephants*, bet tens of thousands of dollars on aftermarket Hatchimals in hopes of flipping them for even higher prices, only to run up against the new restrictions placed on the toys by resale sites.

Spin Master has become one of the major players in the toy industry since its founding in the mid-’90s. On the one hand, they create blockbuster TV show tie-ins (like the PAW Patrol line of canine first responders) and buy up vintage brands like Erector Set and Etch A Sketch. On the other, they build complicated, technical toys for older kids like Air Hogs, a line of flying toy planes and helicopters, and the voice-activated Zoomers menagerie, some of the most advanced toy robots on the market. Hatchimals are the ingenious combination of those two worlds — innovative tech combined with an interface and look designed to appeal to younger kids.

The signature design element is (per the name) the act of hatching. Some Spin Master employees who worked on the project have said that the whole toy was inspired by the freakish popularity of unboxing videos for kids on YouTube — children apparently love watching other kids or adults opening new toys and playing with them, so here’s a toy that can actually unbox itself.

However David McDonald, one of the dedicated designers on Spin Masters’ advanced concepts team that came up with the Hatchimal idea, says that the toy’s origin story is a little less cynical.

“I had always wanted to do something that hatches,” McDonald says. “I always thought that Tamagotchi had dropped the ball — they had a neat idea, but never took it any further, into the real world.”

While researching a whole slate of designs based on biomimicry, McDonald says he saw how a toy could break its way free from an imitation egg: it needed to spin around inside, and then peck like crazy. That presented a materials challenge — how to make an eggshell that a robot could slowly chip its way out of, like a baby chick poking its way out. The team eventually came up with a design that mimics the way that a real egg breaks, piece by piece, by finding the right mix between brittle and bendy plastic, and building a band of structural weaknesses inside of the egg.

But this early Hatchimal was a very different beast. Following the bird biomimicry line of logic, McDonald was trying to come up with a Hatchimal that could actually fly, drawing on Spin Master’s expertise with its flying Air Hogs.

But if this toy was hatching out of its own egg, he thought, then that meant it was a baby. And what do babies do? They cry, they play, they babble, they grow — they need nurturing. So the early-stage Hatchimal lost its functional wings (they still have cute little stubs) and started to get bigger, to be able to fit all the sensors and motors inside necessary to make a lovable, interactive, playful robot pet.

“The mechanism is an odd thing, and takes up a lot of space,” McDonald says. “The character has to power itself to rotate in the egg and peck, and then when you pull it out it has to engage the wheels and start flapping.”

By the time they jammed that all in, they had a roughly Furby-sized chunk of whirring plastic and light-up eyes. But if the point is to get kids to take care of the thing, it has to be adorable and cuddly. Or, as McDonald sees it, a little pathetic.

“We really just draped some fabric over the mechanism, but I think it actually came out brilliant,” McDonald says. Counterintuitively, even though they tested out different levels of plushness, they ended up settling on a shorter, somewhat gnarlier covering for their robot, and designed the eyes to have a slightly sad, worried-looking cast. Even the way it moves when fresh out of the egg is meant to seem helpless and a little lost. “When I look at the poor thing, I want to pick it up,” McDonald says. “It’s like a newborn, and, like a baby, it doesn’t matter if it’s really ugly — you gave birth to it, so you instantly love it.”

To make it seem like it’s truly coming to life in your arms, the team also integrated a secret on switch into the packaging, based on an idea that came from Spin Master’s Hong Kong design team. To remove it from the cardboard and plastic case it’s sold in, you have to take out a few pegs from the bottom of the egg — as soon as they’re out, the Hatchimal’s eyes light up and it starts speaking through the shell.

“We didn’t really think about what it would end up being ahead of time,” McDonald says. “It just sort of appeared as we got deeper into the project.”

On paper, the Hatchimal’s design seems too ambitious for its own good. There’s the IP problem — no one knew what a Hatchimal was before this year, and kids weren’t already smitten with the characters. Then there’s the “blind pack” problem — putting your toy inside an opaque egg is a proven “collect ‘em all” tactic for smaller items, but a $60 (and up) toy that you can’t actually see could deter casual shoppers. And worst of all, there’s the battery life problem — if a Hatchimal sits around on a shelf for a year, there’s a chance its batteries will kick the bucket before the toy has a chance to come to life.

“There were so many reasons not to do it,” McDonald says. But the shelf life of batteries stops being a problem if your product flies off the shelves.

The intense demand and booming secondary market for Hatchimals has prompted some to wonder if the toy’s scarcity is also by design, and speculate that Spin Master is manipulating the supply precisely to drive parents insane. But Sandra Shatilla, the marketing director for the company’s robotics unit, insists that that’s a bug, not a feature. More shipments will keep coming in through January.

And if you can’t wait, you can watch other people take their Hatchimals out of the box, cuddle with it, and see it hatch in their arms — naturally, these things are pretty popular on YouTube.