The Black Cat
A very popular belief and still which lies within us is the black cat as a symbol of bad luck. Black cats were considered evil since the middle ages as it was linked with witches and devils. Nowadays black cat is quite a favorite scary Halloween decoration item used by many.
Thinking about a flying rodent related to Halloween is quite surprising, but it does have history behind it. During old times while celebrating Samhain festival (Known origin of Halloween), Celtic people used to dance around a born fire. As naturally a lot of insects would get attracted to light and the bats used this bonfire as prey nets. They would fly around the bonfire to eat those insects.
Since then bats have been seen as linked to Halloween festival. The rumor of witches using bats blood to fly using brooms made bats look eviler. It made it look more monstrous when bats were known to be bloodsuckers and titled them as vampire bats. In modern days most use bats to decorate their houses for Halloween both indoor and outdoors.