How do your characters react when they see others having their wishes granted but not their own? How do they react when their own are granted? Do they become egotistical monsters or are they grateful for their good fortune and make the most of it without aggravating everyone else?
When a fairy godmother or character of that ilk decides to grant a wish, what makes them do so? I would say pity isn't a strong enough reason. They've got to be able to see something special in the character they're thinking of helping to know that the wish fulfilment will help that character go on and use said wish fulfilment wisely.