A policeman helps Zhezhe wear his uniform. [Wu Yiyao/China Daily]

The initiative was well received, as three roads were sealed off, a dozen of police cars helped clear the way, and tens of thousands of residents as well as hundreds of private cars were involved on Sept 28.

Once in their positions, Zhezhe in police uniform helped direct the traffic and Xuxu was involved in rescuing a resident "injured" in a traffic accident.

Xu Wenjun, the volunteer who acted as the injured person in the accident, said he was tired after lying down on the wet ground for half an hour with his body covered with ketchups, but he was glad to make the two children happy.

In newborns with Prader-Willi syndrome, symptoms include weak muscles, poor feeding, and slow development. As patients grow up, they become constantly hungry which often leads to obesity and diabetes. There is also typically mild to moderate intellectual impairment and behavioral problems.