It was around this time in 1975 that a man dropped by a gift show in San Francisco with an idea that would make him a millionaire.

This is the story of Gary Dahl, inventor of the pet rock.

Dahl’s idea started a few months earlier as a kind of dad joke.

He was out for drinks with some friends, and they were complaining about all the work it took to look after their pets.

Dahl said there were no such problems at his house, because he only had a pet rock.

The only thing he had to do to take care of his pet, he said, was occasionally scrape off the moss.

Everybody laughed, but Dahl got to thinking.

He decided his idea was actually worth trying out as a product.

The rocks were just… rocks, so it would be the concept and the packaging that made the pet rock a product.

Dahl put the rocks in cardboard boxes with air holes, like pet shops used.

And he wrote an “owner’s manual” that suggested people teach their pet rocks tricks, like “play dead.”

When Dahl took the idea to the gift show in San Francisco, people got the joke right away.

By the fall, there were Pet Rocks for sale in the big name department stores.

Over a million people bought them in just a few months.

Dahl was able to open an office for the new company Rock Bottom Productions, where people answered the phone “you’ve reached Rock Bottom…”

The Pet Rock was the very definition of a fad: you can still buy them today, but they don’t sell in huge numbers.

And Gary Dahl was fine with that.

He once said that if the Pet Rock hadn’t become popular, he had a plan B: he would use the leftover rocks to repave his driveway.

Today is Liechtenstein National Day.

The tiny European country is proud of its mountain scenery, its food and drink, and its soccer team.

That team, by the way, often plays in stadiums in other countries that are big enough to fit Liechtenstein’s entire population of about 38,000.

The story of Gary Dahl and the pet rock: From the archives (Mercury News)

Hard Sell: A History of the Pet Rock (Mental Floss)

LITTLE LIECHTENSTEIN ACHIEVE BIG (FIFA)

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Photo by Ruth Hartnup via Flickr/Creative Commons