Old myths are told of the Fey replacing the young and new-born of families with their own. These are called Changelings, and although some speculate that the children are suffering illness or disability, many seem to still believe it. It seems it has a strong belief in Celtic regions, especially Ireland. The Fey would not be above doing so, considering their predilection for 'mischievous pranks'. It is rumoured that this is done so their own child can eventually return with knowledge of the outside world, and vice versa for the human child. Any human child seems to come back having aged very slowly, and usually very young compared to his or hers now elderly parents.