The Pokémon Go craze is sweeping across America. See how the game works, why everyone's so crazy about it, and all the stories that have come from it, from the game's positive impact on depression victims to armed robberies. (Jhaan Elker/The Washington Post)

It began a mere week ago, but Pokémon Go has the world in a creature-finding craze.

As The Washington Post’s Ben Guarino reported, the game has led to robberies and to police-citizen unity, to falling in love and to the discovery of  dead bodies. It has also led to the market value of Nintendo jumping by $9 billion, with shares surging 25 percent in Tokyo on Monday, the Wall Street Journal reported.

So where does such a culturally enormous/resonant/defining moment begin?

As an April Fools’ gag.

As it turns out, John Hanke, chief executive of Niantic Labs, the software development company (and former Google property) responsible for Pokémon Go, was inspired by one of Google’s infamous April Fools’ jokes.

For April Fools’ Day in 2014, Google created a “game” in which users looked on Google Maps for Pokémon a la “I Spy” or “Where’s Waldo.” The Pokémon simply appeared as icons on the classic map screen, the same way a restaurant or a hotel does. There was no actual interaction between user and character. To “catch” one of the creatures, you would just tap on it (the way you would to drop a pin or tap on a coffee shop’s icon to read its hours and reviews).

Accompanying the game was a heart-pounding, highly produced video showing people out in the actual world climbing mountains, riding camels across the desert and taking to the sea in order to find Pokémon. The goal? To win a job as “Pokémon Master” at Google.

The video even features a besuited man in the middle of an urban city, swinging his phone at the air while passersby stare in frightened confusion.

Sound familiar?

If you’ve been hiding under a rock — and are now likely confused as to why so many people are wandering around with their eyes glued to their phones even more than usual — Pokémon Go is an augmented reality game featuring the characters and basic game-play from the popular Pokémon franchise. Augmented reality refers to technology that combines your real-world surroundings with tech, in this case your smartphone.

Players walk around the real world, and digitally rendered Pokémon pop up on their screens at certain locations. Since they don’t know where the Pokémon will be, players are encouraged to wander far and wide.

The game literally spans the globe, so it’s only fitting that Hanke got the idea from Google Maps.

That April, most people played the “game” jokingly, then forgot all about it. Not Hanke.

At the time, Niantic Labs had released Ingress, a game that required users to physically travel to certain places in the real world in order to accomplish their goals. In it, players were tasked with capturing what the game termed as portals, not critters.

Still, the extension of Ingress’s technology seemed inevitable, and Google’s fake Pokémon game sparked the obvious idea.

Hanke certainly noticed it. According to Bloomberg, he asked Masashi Kawashima, Niantic’s director of Asia Pacific, if Google’s fake game “could be done in the real world.”

He wasn’t the only one with such foresight.

As The Verge noted, a commenter on the site’s 2014 story about the April Fools’ prank thought Nintendo and Niantic should team up and combine the former’s intellectual property (Pokémon) with the latter’s real-world augmentation platform (Ingress).

The user, named WickedToby741, wrote the following on March 31, 2014:

The Verge
(Screen grab from The Verge)

Well, that’s exactly what ended up happening.

The trailer for the actual Pokémon Go game focused a bit less on the inherent potential dangers of the game. Where Google’s fake trailer showed users slipping off mountains to catch ’em all, the real trailer included more footage of players quietly waking along the beach.

But overall, Google’s video nearly perfectly predicted the game that would sweep the globe a few years later.

That might seem surprising, but it might not be as serendipitous as it sounds. Forbes reported that Tatsuo Nomura, one of Pokémon Go’s core engineers, was working with Google Maps that April Fools’.

Got questions about Pokémon Go? The Post has the answers:

The first Pokemon game for smartphones is not what I expected

Holocaust Museum to visitors: Please stop catching Pokémon here

Pokémon Go craze sweeps nation: Players find monsters — and injuries, robberies and worse

Australian cops to Pokemon fans: Do not come looking for Pikachu in our police station

A quick look at the Pokemon Go app

Police: Pokemon Go has been used to target armed-robbery victims

Pokemon Go’s unexpected side effect: injuries

What the heck is Pokémon Go? An explainer for the out-of-touch and/or old.

21 pro Pokémon Go tips, from people who spent the whole weekend playing it