It started with a discovery of three mysterious stones in Norwich's Earlham Park featuring a flower, heart and the simple message ready to rock.
But that was enough to entice Taverham mother-of-two Deni Roper to join the new rapidly expanding Facebook page Norfolk Rocks - encouraging families to hunt for hand-decorated stones around the county.
After its creation on August 8, Norfolk Rocks (UK) - based on similar groups in America and Yorkshire - had 700 members which has swelled to over 13,000.
Members, who cannot decorate stones from beaches, share their finds on the Facebook page and connect with other rock hunters.
Some people move the objects into new places but if they decide to keep them they have to create new designs and put them in a special hidden location.
Mrs Roper, 42, who is a health care assistant at the Norfolk and Norwich University Hospital and has two daughters, 12 and 14, said: 'We were paddling in the river at Earlham Park and the three rocks were hidden in the trees. It was kind of magic. We didn't expect to find anything there. We just stumbled across them. It was fun and exciting.'
Since then Mrs Roper's daughters, Livi and Maya, have created about 25 different designs, including Cbeebies cartoon characters, dragons, the Very Hungry Caterpillar, Peppa Pig and Winnie the Pooh.
They have also created a depiction of the cult Netflix series Stranger Things and American wrestler and actor Dwayne Johnson - known as the Rock.
All their pieces of art have been hidden around the Taverham and Thorpe Marriott area in woodland, play parks and outdoor nooks and crannies.
'It is a really fun thing for children to do. It is a good way to get children out in the sunshine. It is interesting to see where all the rocks end up. The craze seems to have spread very quickly,' Mrs Roper added.
Founders of the group, known as Rocky Rainboe - who are actually a mother and 16-year-old daughter from Tacolneston - said that Norfolk Rocks has inspired similar groups in other counties, including Suffolk.
Before Norfolk, there were already groups in Yorkshire and America.
It is estimated there are thousands of rocks as part of the Norfolk network which as 'grown at an astronomical rate'.
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