I heard this story from a lady at the park whose son plays with Owen and Stewart sometimes.
She said they were at the mall and passed a fountain.
"Mommy," her son said, "Give me a quarter, I want to make a wish."
So he threw the quarter in and wished for Scooby-Doo toys.
Then she threw a quarter in and wished, outloud, that her son would "be a good boy and listen to his Mommy."
"Mommy," he said. "Can I have another quarter?"
"Sure," she said, and gave him one.
Tossing it into the fountain, he said "I unwish my Mom's wish."