Ancient Japanese legend promises that anyone who folds a thousand origami cranes will be granted a wish by the gods.  The crane is one of the holy creatures and is said to live for a thousand years.  That is why 1000 cranes are made, one for each year. In some stories it is believed that the 1000 cranes must be completed within one year and they must all be made by the person who is to make the wish at the end.