Pokemon Go is the latest craze to take over the world.
In little more than a week, millions of people around the world have taken up the challenge of fighting the monsters in public places, adding $10 billion to Nintendo's share value, and prompting police warnings about the dangers of injury - and worse - as people fixate on their mobiles.
Of course, fads are nothing new. Here are some others. How many others do you remember?
From around 2008, people began lying face-down on anything, photographing it and uploading to social media. It lasted a year or so before falling flat.
In the 1950s, this child's plaything - which had existed for centuries - was suddenly taken up by adults with people twirling on TV, in movies and on song.
The craze has come full circle - and kids still find it great fun.
The numbers puzzle game first appeared in France in the 1800s then various US newspapers in the late 1970s but only became popular in the 2000s after the Japanese adopted it and exported it to the world. As they do.
On a scale of 1-10, this is easily a 10 for most disgusting fad listed. It began with American college students in the 1920s and '30s and caught the public imagination for about five seconds before vanishing again.
Only the Japanese would invent a handheld digital pet in lieu of the real live, breathing thing. These toys had to be petted, "fed" and cared for just like the real thing. Until the battery ran out, anyway.
Of all the dance crazes to sweep the world - and there have been plenty - this Spanish creation from the 1990s may be the only one which featured the then-Treasurer on national television strutting his stuff.
In the 1980s - when it was hip to be square - this mind-bending invention by the Hungarian maths professor of the same name seemed to be in the hands of everybody, trying to solve the puzzle. It's still popular today.
A group of seemingly random people gather in a public place, perform a dance routing then disperse. In the early 2000s, these happened everywhere, especially shopping centres.
Dating from ancient Greece, yo-yos bounced back into popular culture in the 1960s and have enjoyed up and down popularity over the years since.
Grab a rock, put it in a box. Sell it. Genius mid 1970s marketing from America which quickly sank like a stone again. But not before "inventor" Gary Dahl (who got the idea while drinking beer) sold 1.5 million for $4 each and made a fortune. And they thought he had rocks in his head.