You better watch out - Santas and Grinches will soon be hiding in Koshigaya Park.
Hordes of Sydney-based rock enthusiasts will descend on the Campbelltown park this weekend to leave hundreds of painted stones for locals to find.
Minto grandmother Maddy Sen created the NSW Rock's Facebook page, a 68,000-strong community of rock painting enthusiasts, and has selected Koshigaya Park as the location for their latest Christmas-themed drop.
She said she was inspired by a similar group in Western Australia a few years ago, and was shocked at just how quickly the NSW group grew.
"When people stumble across these rocks they just feel happy," she said.
"I saw that this was happening in Western Australia and I thought we could do the same thing here.
"I started the group in May, 2017 and we've already got 68,000 people from all over the state.
"It just seemed like an awesome idea and it's a great way to do something with the family."
Ms Sen's daughter and grandchildren are also involved with NSW Rocks and will join her for the drop at Koshigaya Park this Saturday and Sunday.
She said the main aim of the group was to bring some unexpected joy into people's lives.
"They can just brighten up people's days," Ms Sen said.
"Some of our members write messages like 'be brave' or something else to inspire people.
"They might be hidden in a bush or in the fork of a tree.
"Some people take them home while others leave them for more people to find."
Rocks will be dropped in 80 locations across the state this weekend, with Koshigaya Park being the closes for Macarthur residents.
All rocks will be painted with Christmas images - like Santa Clause, the Grinch, reindeer, snowmen and more.
Ms Sen said many NSW Rocks members were older, retired people who enjoyed filling their days painting rocks. She said rocks were usually purchased from stores like Bunnings.
She invited any interested locals to pop down to Koshigaya Park this Saturday and Sunday and take part in the event, or visit later to find the hidden rocks.