The stone dolls are rock formations that are caused by long-term erosion of the volcanic rock. Harder, compact stones (ignimbrite, andesite) slowly erode and protect the softer tuffs underneath.
Of course there is also a legend that sounds much more exciting and obvious ;-):
According to legend, a long time ago a great tragedy occurred in the village of Kuklica. A boy, a great builder, bricklayer, but also an impostor and Casanova, lived in the village of Kuklica. One girl was in love with him, but he married another, and the disappointed girl cursed the newlyweds.
In the legend, the bride was a richer girl from the lower quarter of the village, while the girl in love who uttered the curse was a more beautiful but poor girl from the upper quarter.
When the wedding day came, everything seemed to be in order: the bride and groom gathered, the other guests came, the celebrations began. The moment the bride and groom kissed, the curse came true and all wedding guests were petrified.