I got to see TEF's foggy weather =D happy~ And... Is it me or there are bats? o.o

De Drinkplaats mystery~
Do you know when you turn into a flying animal after drinking frm the water of De Drinkplaats and you fly over the fountain, a rock falls out of the sky? It just lands in front of you then disappears. Does anyone knows what the rock does? Cause it looks pretty interesting ^^