According to old finnish folklore, having a wild animal wander into your house is an omen of death. The bigger the animal, the more imminent the death. A small bird, like a sparrow or a finch, is a sign that someone who lives in the house will die within the year. If the animal that has somehow made its way inside the house is a small mammal like a hedgehog, or a larger bird like an owl or raven, would mean that death is coming to visit in the next few months.
Massive megafauna, like a fully-grown moose or a bear, is a sign that someone will probably die within the next 20 minutes.
This one doesn't get to stay hidden in the replies.
