Eggs
There are many superstitions surrounding eggs, but one of the weirdest is that if you break an egg, you need to crush the ends of the shell as well — if you don't, a witch will gather up the shell, use it to build a boat and then start a huge storm out at sea.
Another (and less odd) superstition holds that if you ever break an egg and it has two yolks within, you'll have twins.