When Polish people sit down for their Christmas Eve dinner, they always serve 12 courses at the meal, one course for each of the 12 Apostles. To assure good health during the following year, everyone in the family must taste all 12 courses!
On Boze Narodzenie, which is Polish for Christmas, one empty seat is always left at the table, in case a stranger should come by. And an odd number of persons at a Christmas Eve dinner means bad luck for all.