Pet Rocks 

The Pet Rock was probably the biggest toy fluke of the 20th century. Can you imagine people today buying a rock decorated with animal features? 

Created in 1975 by an advertising executive called Gary Dahl - he brought the small smooth rocks from a Mexican beach and packaged them in a tiny box with air holes. The true genius was inside; a rock nestled on a bed of straw with a tiny book explaining how to train, play with and even house-train your pet rock.

Though initially just plain rocks, they were eventually sold with faces painted on, often sold as a group of pebbles, symbolising a small family or a 'rock' band. By Christmas 1975, two and a half tons of rocks had been sold and 75% of all daily newspapers in America had run Pet Rock stories.

A million rocks sold for $3.95 each in just a few months, and Gary Dahl - who decided from the beginning to make at least one dollar from every rock - had become an instant millionaire.

Copycat rocks flooded the market, including one cleverly marketed as "the Original Pet Rock," and dozens of quick-buck entrepreneurs joined the action selling such ancillary fun as Pet Rock Obedience Lessons and Pet Rock Burial-at-Sea Services. 

Immediately after Christmas 1975, Gary Dahl himself relabelled leftover Pet Rocks as Valentine's Day gifts for loved ones in need of a low-maintenance pet, but the Pet Rock quickly became last year's fad.