I first heard of the idea of a pet rock through Spongebob. I thought it was just a running gag featured on the show until I learned that Pet Rocks were an actual thing in the 70s.
Here’s how Gary Dahl, an advertising executive, came up with the idea for pet rocks.
Gary Dahl came up with the idea in a bar while listening to his friends complain about their pets; this gave him the idea for the perfect “pet”: a rock. A rock would not need to be fed, walked, bathed, or groomed, and it would not die, become sick, or be disobedient. Dahl said that they were to be the perfect pets and joked about it with his friends. Dahl took his “pet” idea seriously, however, and drafted an instruction manual for a pet rock. The manual was full of puns and gags that referred to the rock as an actual pet.
Dahl sold over a million pet rocks.
This is a great example of a bad product, with great marketing.