how is the theme of the monkeys paw and sylvester and the magic pebble similar

"The Monkey's Paw" and "Sylvester and the Magic Pebble" are both stories that involve an element of magic as well as a hint of darkness. The theme of each of these stories is to be careful what you wish for.
In "The Monkey's Paw," the visitor, Sergeant-Major Morris, warns Mr. and Mrs. White as he is telling them about the paw. He states of the man who put a magic spell on the monkey's paw, "He wanted to show that fate ruled people’s lives, and that those who tried to change it would be sorry." Mr. and Mrs. White learn that their first wish is granted at the expense of their son's life. Theirs is not a happy ending.
In "Sylvester and the Magic Pebble," Sylvester, a donkey, wishes to become a rock to save himself from a hungry lion. Once the wish comes true, he learns that since he is no longer holding the magic pebble, he cannot wish again to be a donkey. Sylvester almost gives up hope and resigns to just be a rock. However, the ending of this story is a happier one as Sylvester is able to become a donkey again and reunite with his parents.