White Rabbits - Black Figures

Another English text book topic was practically illustrated during the English lesson. We were learning about British superstitions when suddenly two black  figures entered the classroom. All students started frantically to look for a button.  In Poland, when you see this person,  you have to hold your button and make a wish. We don’t say ‘white rabbit” three times on the first day of each month as the British do. What about you?  What superstitions are there in your country? And do you know who entered our classroom?