Just cause:
Today, black cats are as much a symbol of Halloween as are pumpkins, ghosts and witches. But this wasn't always the case.
In fact, unlike most Halloween customs, which date back to the ancient Celtic celebration of Samhain, the black cat association is a more recent addition.
In the early Middle Ages, cats began to be associated with witches. While the exact reason for this association is not clear, historians suppose that it has something to do with a cat's nocturnal nature.
Some in the Church believed that witches became cats at night. Others associated cats with witchcraft because their eyes glow at night, a sign of evil.
The powerful association between witches and cats, especially the "sneaky" black cat, persisted throughout the centuries. So when modern celebrations of Halloween evolved to include images of the wicked witch, the black cat was right behind her.
"Cats are intended to teach us that not everything in nature has a function." - Unknown