Wikisimpsons - The Simpsons Wiki
When Homer bought it from the seller, he warned Homer about the misfortune it will bring. Homer didn't care and bought it anyway. He then took it back home.
When arguing over who makes the first wish, Maggie takes the paw and wishes for a new pacifier, delivered by a man in a limo. Bart then takes the paw and wishes for the family to be rich and famous. Everyone starts to hate the family because of their fame and everyone is sick of them.
Lisa then wishes for world peace. This works, except Kang and Kodos then invade Earth, and enslaves Springfield. Homer then makes a wish for a turkey sandwich, explaining exactly how he wants it. However, the turkey was a little dry so Homer's wish failed. Homer then gives the paw to Ned Flanders and Ned becomes a hero after wishing the aliens out of town, meaning his first wish didn't bring him misfortune. He then wished that his house was a castle, once again successfully.