King O'Toole and His Goose
King O'Toole a fine old king grew old and the poor king was obliged at last to get a goose to divert him, but the goose got stricken in years like her master and couldn't divert him no longer, and then it was that the poor king was lost entirely. Saint Kavin comes to talk to the King saying he can make things as good as new and will do so for King O'Toole's goose. Saint Kavin wants all the land the goose flies over after she is made brand new for the service he will do and the King agrees. The saint reveals his identity and tells the king he was testing him. The saint blesses him and his goose for the rest of his life and the goose dies by an eel.
Beth Gellert
Llewelyn had a favorite dog, Gellert. When the Llewelyn had returned from a hunt he saw Gellert greeting him with a blood-stained mouth and a blood trail that ran to his son's nursery. He could not find his son anywhere and kills Gellert thinking the dog killed his son. Llewelyn found his son under the cradle and the body of a dead wolf who had tried to kill his son who was protected by Gellert the dog.
Brewery of Eggshells
There once lived there a man and his wife, and they had twins and one day when she was gone she saw two old elves of the blue petticoat crossing her path though it was midday which frightened her so she raced home. She found her twins as though she had left them. But after a time, the good people began to suspect that something was wrong for the twins didn't grow at all, and these were not her children. The woman saddened decided to consult the Wise Man of Llanidloes. He tells her on reaping day clear out the shell of an egg and boil some potage in it, and then take it to the door like an offering for the reapers. If the twins say things beyond the understanding of children, go back and throw them into Lake Ebyr but if not do nothing. She threw the fake children into the lake and the goblins came and snatched them back and left her real children in their place.
Bibliography:
Celtic Tales: Fairies, leprechauns, ghosts, and goblins, along with a Celtic version of "Snow White."