Pet rocks became a popular novelty item in the 1970s. They were rocks that were sold in little boxes with air holes, along with instructions on how to care for them. The idea behind pet rocks was that they required no feeding, grooming, or training, making them the perfect low-maintenance pet. People would often give their pet rocks names and take them on pretend walks or play with them. The fad eventually died out, but pet rocks remain a nostalgic symbol of the 70s.