The Japanese video game series Pokémon turned 20 years old last Saturday, Feb. 27.

Of course, “Japanese video game series” feels like a complete cop out and loss of journalistic integrity. The name carries the weight not just of card/video games, TV shows, manga, books, fan-fiction, etc., but of an entire mythopoeic paradigm that captured the youth of the west.

The paradigm runs thus: introduce successful product in medium A. Expand success to semi-related medium B. Further expand to unrelated medium. Wash, rinse, repeat. Think of medium A as video games, medium B as card games, and C as television. The behemoth that is Pokémon was not just a successful merchandising stunt; it permeated between interactive and passive entertainment so fluidly that we—the youth caught in this marketing blitz—abandoned the limits of fantasy.

The word “Pokémon” itself is a fusion of “pocket” and “monster,” thought up by the game’s creator Satoshi Tajiri. And a Pokémon (n.) is just that: a monster that, when properly contained, can fit as an accessory in one’s pocket. (The mechanics of which involve an imaginary contraption known as a Poké-Ball.)

Tajiri was inspired by his time spent collecting insects as a child, and developed the idea of creatures—similar to animals, but with fantastical powers—that one could collect. The somewhat violent trajectory that the early-90s video game scene was shaping up to be informed the battling aspect of Pokémon: you make the critters fight.

Make your critters fight hard enough and they “evolve” into bigger, badder, stronger critters. So the game is guilty of basic Skinner-Box logic: complete task, get stronger/better, complete harder task.

But notice the use of the word “evolve” in the sentence above. The word is used in the games to describe an instantaneous physical transformation of your pocket-monster, and has little to do with genes or geological time or natural selection.

What started off, in all probability, as a translation error has become codified as one of the most ubiquitous slangs in the 21st century American dialect. If you are not convinced, go into Microsoft Word and type in “Pokemon” (e without the acute). Then watch as the red you-messed-up squiggly politely corrects you to “Pokémon.”

So, if it’s just a Skinner-Box level-up machine, why the cultural domination of the late ’90s?

Where Pokémon the game departs from other Nintendo successes—think Kirby, Mario, Zelda et al.—is what happens after the game is complete.

In the original game, there were 151 unique species of pocket monsters you can collect. Twenty years and six generations of Pokémon later, and there are more than 700 of the critters. They were introduced to us methodically, a few at a time, over the course of decades. We have had the time not only to learn every face and name, but their strengths, weaknesses and personalities.

You can only train and battle with six at a time. Which six you choose out of the hundreds available is your call—and not all pocket monsters are created equal. Some are stronger than others. The obvious choice is to pick out the six best fighters you can find.

But the longer one plays, the more one comes to realize: the strongest monsters you can collect might not be your favorites. Perhaps you are a fan of butterflies. You are in luck: one such Pokémon is a repurposed telekinetic butterfly. Perhaps you like horses. Pokémon has one that can shoot fire.

And the end result is: anyone who sticks with the game long enough to play it repeatedly begins to learn the difference between completing a game efficiently and having fun. Perhaps you did not catch a Pikachu the first time around. Go back, and find one. They are out there, waiting. The best perk: you can even nickname them. There might be infinite computer-generated fire-horses out there, but only one has the name you gave it.

And the game is not a simple Tolkien-esque fantasy rewrite. The world of Pokémon exhibits subtle moments of superb sci-fi capabilities (such as the aforementioned Poké-Ball’s ability to shrink a monster to the size of a fist), while the fauna command the elements of nature (such as fire, water, earth or telekinesis). Nothing is excessively fantastical. The Poké-world is unassuming in its strangeness. It does offer cheap explanations for why you should accept its reality. It simply invites you in.

I still have memories from the immediate months after the game’s release. The TV series had started and most kids were watching it. My friends tried to explain to me what a “Ditto” was. (For the uninitiated: every different type of pocket monster has a name, and all monsters of that type share that name.) They described a piece of gum that could turn into anything. I imagined an unchewed rectangle of Extra brand gum turning into a car.

This is not, of course, what a “Ditto” is. (Go ahead and Google “Ditto” if you are lost; the cartoon pink blob with a face is the subject matter.) I soon found that out. And a few weeks later, there were no more kids who did not know what a Pokémon was.

Of course every generation must cede ground to the new. But the mythopoeia has not been lost to time. Show the face of a Pikachu to any human between, let’s say, ages 10 to 50 in America, and they will recognize it, even if they cannot name it.